5 CASE HISTORIES OF HIGHLY INVASIVE WOODY SPECIES IN THE TROPICS
5.1 INTRODUCTION
The Invasive Woody Plant Database, like any ecological database, can be used to provide an overview of invasion by woody plant species as presented in the previous section. However, information on a ecological database cannot provide a comprehensive picture of the complex interactions of ecological, environmental and historical factors affecting plant invasions. Here, to provide further insight into the subject we present a series of case histories of woody plant invasions. Due to the limited number of well investigated cases only a small subset of the species found in the Invasive Woody Plant Database can be reported in detail.
Cronk & Fuller (1995) give detailed accounts on six species dealt with here, namely Clidemia hirta, Lantana camara, Melaleuca quinquenervia, Mimosa pigra, Passiflora mollissima and Pittoporum undulatum as well as another tropical woody plant Psidium cattleianum. Cronk & Fuller have used a different approach to produce their account focusing more on the control and management of the species, botanical description as well as reported cases of introductions and invasions.
In Australia, substential accounts of Acacia nilotica (Mackey 1996a), Cryptostegia grandiflora (Mackey 1996b), Prosopis spp. (Csurhes 1996) and Senna obtusifolia (Mackey et al. 1997), with special refrence to Queensland, have been produced. The Department of Primary Industry and Fisheries of the Northern Territory publishes 'Agnote' which consists in a large number of short accounts on weeds of the Northern Territory and include a number of invasive woody plants (e.g. Prosopis limensis (Gracie 1992), Mimosa pigra (Smith & Miller 1991)). 
Other useful species accounts may be found in Anon. (1980, 1983) and Holm  et al. (1977).
A number of Web sites have species accounts and the relavant ones are:
Cryptostegia grandiflora: http://leaky.rock.tap.csiro.au/facts/woody.html#Rubbervine
Parkinsonia aculeata: http://leaky.rock.tap.csiro.au/facts/woody.html#Parkinsonia
Zizyphus mauritiana: http://leaky.rock.tap.csiro.au/facts/woody.html#Chinee
Invasives in Hawaii: http://www.botany.hawaii.edu/faculty/cw_smith/aliens.htm
5.2 SPECIES DESCRIPTIONS
In each species account information on a number of species attributes and on various environmental and ecological characteristics of the native and invaded ranges is reported. Each account is divided into five main sections and the details are given below. Wherever necessary, assumptions made, limitations to information supplied and required explanations are indicated.
Species characteristics
Synonyms of botanical names are included only if they have been used in TREE-CD over the past five years.
Life form, size, lifespan
Taxonomy, variation and plasticity
Reproductive biology
Resilience and resistance
This section focuses on the species ability to respond to physical damage, fire, drought, flooding, pests and diseases 
Environmental requirements and successional status
Products and uses
Status in native range
Range and abundance
Climate
Site requirements 
Weediness
Pests and diseases
Status in invaded regions
In this section all information given refers to the most highly invaded region unless stated otherwise
History of introductions and intensity of invasions
Patterns of invasion and time-lag
Site and climate
Floristic region and vegetation types
Pests and diseases
Impact on ecosystem
Impact on humans and related activities
Control
Ecological differences 
Existence of ecologically equivalent species and competitive
interactions in invaded regions
Ecologically equivalent species should exhibit great similarities in species attributes (e.g. lifeform, size, lifespan, fruit type, dispersal agent), in site and climatic requirements as well as in successional status. Only detailed investigations can differentiate ecologically equivalent species. A good example is provided by the two European timber trees Acer pseudoplatanus L. and Fraxinus excelsior L. which differ mainly in terms of duration in seed dormancy, tolerance to flooding, susceptibility to grass competition and variation in latitudinal and altitudinal distributions (Binggeli 1992). Another example is the case of  Quercus robur L. and Q. rubra L., the latter invading forests dominated by the former, reported by Barkman (1988).
Differences in status and ecology between invaded and native ranges 
Selected references 
Up-to date key references on the ecology of a species in its native and invaded ranges as well as key references on other subjects such as botanical description, taxonomic treatment, species bibliographies, diseases and biological control are given. Each reference is annotated as follows: * reference on invasion, ** key reference on invasion; • reference on native range, •• key reference on native range; # references on other subjects relating to the species including: botanical description, pest and diseases, reviews etc...
5.3 SPECIES ACCOUNTS
The species accounts of 18 tropical invasive woody plant are available and are listed in Table 5.1.
Table 5.1. Woody plant species for which a detailed account is available (S = shrub, sT = small tree, T = tree and V = vine).
SPECIES	FAMILY	LF	Native region	Invaded regions	Habitat invaded	
						
Acacia nilotica	Mimosaceae	T	Africa-India 	Australia, Indonesia 	grassland	
Casuarina equisetifolia	Casuarinaceae	T 	Australasia	Florida	coastal sands	
Cecropia peltata	Cecropiaceae	T 	neotropics 	Africa, Asia	disturbed areas, forest gap	
Chromolaena odorata	Asteraceae	S 	neotropics 	Africa, Asia	fallow, logged forest	
Clidemia hirta	Melastomataceae	S 	neotropics	Oceanic islands	disturbed areas, forest	
Lantana camara	Verbenaceae	S 	neotropics 	tropics	pasture, plantations	
Leucaena leucocephala 	Mimosaceae	sT	C. America 	Pacific islands	disturbed areas	
Maesopsis eminii	Rhamnaceae	T	Africa	East Africa	natural & secondary forest	
Melaleuca quinquenervia	Myrtaceae	T	Australia	Florida	swamp	
Miconia calvescens	Melastomataceae	sT	neotropics	Pacific islands	forest	
Mimosa pigra 	Mimosaceae	sT	neotropics	Australia, Thailand	flood plain	
Myrica faya 	Myricaceae	sT	Atlantic Isl.	Hawaii	lava flows	
Passiflora mollissima 	Passifloraceae 	V 	neotropics 	Hawaii	forest	
Pinus patula 	Pinaceae	T	Mexico	East Africa	forest, grassland	
Pittosporum undulatum 	Pittosporaceae 	T 	Australia	Jamaica	forest	
Psidium guajava 	Myrtaceae	sT	neotropics 	Pacific islands	pasture, forest	
Schinus terebinthifolius 	Anacardiaceae	sT	S. America 	Florida	disturbed areas, grassland	
Ulex europaeus 	Papilionaceae	S 	W. Europe	mountain tropics	pasture	

Acacia nilotica (L.) Del. (Mimosaceae)
A. arabica (Lam.) Willd.
A variable and widely used tree from Africa and the Indian subcontinent. Subsp. indica, introduced to northern Australia, has spread into dry grassland, slowly at first, but then with population explosions during wet years.

Species characteristics
Life form, size, lifespan
Thorny small tree growing to a height of 7 m. Lives at least 60 years.
Taxonomy, variation and plasticity
Nine sub-species are recognised. Hybridization between the various ssp. occurs and has been influenced by human's seed dispersal. Within the A. nilotica complex the pods are very variable.
Reproductive biology
The yellow sweetly scented flowers are nectarless and found in round heads. Most flowers are functionally male with a few hermaphrodites and are mainly bee-pollinated. Pods are indehiscent. Seed production is high (up to 175,000 seeds/tree) and yearly provided water is plentiful like along water courses. In Kenya seed set per pod was 10.8 and trees produced between 153 and 34,000 seeds. It forms large seedbanks and in Australia the half-life of seeds is 10-12 months. 
Leaf production and fall are affected by rainfall whereas temperature affect flowering and fruiting. In Sudan A. nilotica flowers irregularly but generally between June and September and seed fall takes place from march to May. In Australia trees flower from March to June and green pods are produced within four months but ripe pods fall from November to February. Most of the leaf fall occurs during the dry period when the tree bears green pods.
Resilience and resistance
Species is sensitive to frost but is tolerant of grazing, drought (< 2 years), fire and salinity.
Environmental requirements and successional status
Requires water for seed germination and seedling establishment. Can regenerate under pioneer woody plants in seasonally flooding habitats and subsequently outcompete them.
Products and uses
Extensively used as browse, firewood and timber. The bark and seeds are a source of tannin while bark, roots and flowers are used for medicinal properties. The gum is sometimes used. The wood is suitable for paper production. Planted for forestry or reclamation of degraded land.
Status in native range
Range and abundance
Native to India, Pakistan and much of Africa where it is often dominant.
Climate
Grows in areas where the mean monthly temperature of the coldest month is above 16°C. It tolerates a wide range of rainfall from less than 350 mm to more than 1500 mm or more per year.
Site requirements 
A. nilotica subsp. indica is commonly found on soils with a high clay content, but in areas of higher rainfall it may grow on deep sandy loam. Often found growing close to waterways on seasonally flooded river flats. In Sudan, along the Nile, regeneration has been reported as occurring once every ca. 15 years following high floods. 
Weediness
With the exception of A. nilotica spp. kraussiana in southern Africa, there does not appear to be much evidence to show that the tree is weedy in its native range.
Pests and diseases
Many wild mammals feed on seed pods and a large number of insect species attack the mature seed.
Status in invaded regions
History of introductions and intensity of invasions
A. nilotica subsp. indica, native to the region spanning from Ethiopia to Burma, was introduced to Iran, Vietnam, the Caribbean and Australia. Introduced to Australia around 1900 as a shade tree along bore drains in Queensland. Found elsewhere in Australia but the distribution is limited by frost. Around 1960 it was found in 7% of the Mitchell grassland areas and by the mid 1980s it covered 6.6 million ha or 25% of the area. Its distribution and population densities are still increasing. Since 1969 introduced to the Baluran National Park (Java, Indonesia) as a firebreak and is spreading vigorously.
Patterns of invasion and time-lag
Dramatic increase in A. nilotica, particularly on town commons, took place in the 1950s as a result of a series of years with above average rainfall. Following this population outbreak the species was declared a noxious weed. Instead or removing the plant as required, many landholders continued to plant them along open drains distributing artesian water. The constant water supply ensured fast grow rates and the production of large seed crops, which were spread by cattle throughout the surrounding countryside forming large seedbanks. During a second period of above average rainfall in the mid-1970s germination of the seedbank occurred and resulted in a 1000 fold increase in A. nilotica populations. The highest densities of A. nilotica are found on properties which had the tree planted along its drains prior to the 1970s and had cattle rather than sheep grazing. In the 1980s a prolonged drought has reduced tree density in some areas by up to 80%. In Indonesia it invaded, with apparently no time-lag, wild grasslands.
Site and climate
Clay soils in dry tropics.
Floristic region and vegetation types
In northern Australia, A. nilotica is spreading into grassland dominated by Astrebla spp.
Pests and diseases
Two insect species, including one Coleoptera introduced as an attempt at biological control, eat the seeds unless they are quickly ingested by mammals soon after ripening. The passage through the digestive track of cattle apparently make seeds nearly immune to insect attack.
Impact on ecosystem
The vast grasslands of northern Australia are changed into woodland. In Indonesia it is altering the physiognomy of the invaded ecosystem and depriving native mammals of grazing grounds.
Impact on humans and related activities
The invasion reduces the livestock carrying capacity of Queensland's Mitchell grasslands. It may have an impact on the number of tourists frequenting the Baluran National Park as most visit the park to view large herds of herbivores.
Control
In Indonesia both mechanical and chemical control have been practised and the former was found to be more economical. In Australia a biological control programme has been initiated.
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
The invaded ecosystem is grassland and therefore is treeless. This is an example of a lifeform hitherto absent being able to spread. 
Differences in status and ecology between invaded and native ranges 
A. nilotica appears to suffer from fewer insect pests, particularly seed pests, in Australia than in native range.
Selected references 
* Alikodra, H.S. (1987) Tanaman eksotik akasia (Acacia nilotica) dan masalahnya bagi ekosistem savanna di Taman Nasional Baluran. Duta Rimba 13(79‑80), 30‑34. 
** Brown, J.R. & Carter, J. (1998) Spatial and temporal patterns of exotic shrub invasion in an Australian tropical grassland. Landsc. Ecol. 13, 93‑107.
** Carter, J.O. (1994) Acacia nilotica: a tree legume out of control. In Gutteridge, R.C. & Shelton, H.M. (Eds) Forage trees as legumes in tropical agriculture, pp. 338‑351. CAB International, Wallingford.
#• Fagg, C.W. & Greaves, A. (1990) Acacia nilotica 1869‑1988. Annotated Bibliography ‑ CAB International F42, 1‑81.
** Mackey, A.P. (1997) The biology of Australian weeds. 29. Acacia nilotica spp. indica (Benth.) Brenan. Pl. Prot. Quart. 12, 7‑17.
• Marohasy, J. (1995) Prospects for the biological control of prickly acacia, Acacia nilotica (L.) Willd. ex Del. (Mimosaceae). Pl. Prot. Quart. 10, 24‑31.
* Suharti, M. & Santoso, E. (1989) Analisa biaya pengendalian Acacia arabica di Taman Nasional Baluran Jawa Timur. Bul. Pen. Hutan 505, 1-8.
# Tybirk, K. (1989) Flowering, pollination and seed production of Acacia nilotica. Nord. J. Bot. 9, 375‑381.
Pierre Binggeli
May 1997

Casuarina equisetifolia L. (Casuarinaceae)
Drought and salt resistant tree from Australasia widely planted in the tropics and sub-tropics. In Florida it is spreading on sandy shores and in areas disturbed by hurricanes. It forms dense stands and destroys reptiles breeding sites.

Species characteristics
Life form, size, lifespan
Evergreen tree reaching a height of 30-40 m.
Taxonomy, variation and plasticity
The var. equisetifolia and var. incana Benth. differ in height and stem straightness the latter being smaller and a poorer stem form and a more open canopy. Many morphological features are very variable.
Reproductive biology
The species is monoecious or dioecious with 2-3% of the individuals being monoecious. Males start to flower in the second year whereas females one year later. wind pollinated. The fruit is like a woody cone, 1 to 2 cm in diameter. They contain 70-90 seeds and take 3-4 months to mature. The seeds (achenes: 600 to 2000 seeds per g) have a membranous wing and are wind-dispersed. They can also be water-dispersed. Germination rate varies between 30 and 84 % but seeds are only viable for a few months. Usually, there are two main flowering and fruiting seasons although some fruits are often produced all year round, but in Hawaii and Puerto Rico flowering and fruiting are irregular. Seeds are produced annually.
Resilience and resistance
Adaptations to dry climate include scale-light verticillate leaves and modified needle-like twigs for reducing transpiration by means of sunken stomata lying in grooves, hairs, thickened cells and cuticle. Roots have nodules with symbiotic nitrogen fixing bacteria. It is not resistant to frost and has low fire tolerance but is salt tolerant. Adapted to growth on sand dunes as lower branches root and upright branches develop. Stilt roots and prop roots are sometimes in waterlogged areas. Does not suffer from browsing. When cut the tree sprouts profusely. It is often propagated by cuttings and in India by layering from low spreading branches. 
Environmental requirements and successional status
A light demanding species which needs open sites for establishment, free from plant competition. It forms permanent stands in saline coastal environments and sand dunes.
Products and uses
The strong and heavy wood is durable in the ground and submerged in saltwater. It is a very good firewood and fine for charcoal whereas it is not adequate for fine carpentry. Widely planted for amenity purposes, coastal reclamation, medicinal purposes, tannin, dyes, pulp and timber.
Status in native range
Range and abundance
Native to Australasia. In Australia the var. equisetifolia occurs along a narrow coastal strip of tropical Australia whereas var. incana extends south (to 32°S). Altitudinal range: sea level to 100 m.
Climate
Var. equisetifolia occurs in the hot humid and sub-humid zone (monsoonal) whilst var. incana is found in the warm sub-humid zone. Frost occasionally occur inland in the most southern part of var. incana range. Typical rainfall lies between 1000 and 1500 mm a year.
Site requirements 
Found in dry and exposed habitats, typically coastal sand dunes. Var. incana may also occur around the bases of rocky headlands. Usually it is the only woody plant in vegetation dominated by grasses and herbs. Sometimes found associated with eucalypts.
Weediness
Not recorded.
Pests and diseases
Seeds are carried off in large quantities by ants. Seeds and seedlings are attacked by insects and crabs. It suffers from many fungal diseases.
Status in invaded regions
History of introductions and intensity of invasions
In Florida, var. incana Benth., was introduced around 1900 and planted by farmers and fishermen near homesteads and citrus groves for shade or as windbreak. In the 1930s trees planted to reclaim swampland as it was erroneously thought that the trees would dry the swamps. Extensively planted for reforestation in many parts of the world mostly on coastal dunes as well as in new urban areas of Malaysia. It was introduced to India as early as the 1860s but its provenance is unknown.
Patterns of invasion and time-lag
C. equisetifolia first started to spread along shell beaches and open sands, and by the 1950s it was only found in scattered locations in the Everglades National Park. Two successive hurricanes in 1960 and 1965 created the disturbed areas necessary for the rapid spread of C. equisetifolia. The species didn't survive well in areas of prolonged flooding and its spread inland was restricted by fire.
Often found in nitrogen deficient soils in urban areas where the top-soil has been removed. For instance, with Acacia auriculaeformis, it dominates the pioneer vegetation in urban areas of Malaya.
Site and climate
Floristic region and vegetation types
Coastal herbaceous swamp and broad-leaved hammock communities.
Pests and diseases
In Malaya it does not appear to suffer from pests although it harbours Icerya purchasi, a pest of orange and lemon. Many pathogens threaten extensive plantations in many parts of the world. In India a stem borer kills shoots and seedling damping-off by Rhizoctonia spp. occurs in nurseries. In Puerto Rico natural regeneration is rare because ants eat nearly all the seeds. 
Impact on ecosystem
In Florida its roots can prevent turtles from digging nests for their eggs, and sometimes turtles are trapped by the roots. On coastal areas subject to wave erosion, toppled trees act as groynes, increasing loss of sand. Under the dense shade cast by C. equisetifolia canopy a thick mat of twigs is formed which prevents regeneration.
Impact on humans and related activities
The large quantities of air-borne pollen cause respiratory irritations. In Florida this large tree (up to 30 m) is considered as a public safety hazard. During hurricanes the fall of C. equisetifolia can damage property or block evacuation roads. In northern areas frost-killed trees become a nuisance due to the fall of branches and crowns. It often forms dense stands which are nearly impossible to walk through.
Control
Its threat to the Everglades National Park was quickly realised and a control programme was initiated. Seedlings were easily uprooted and larger trees killed by cutting or girdling and treated with the herbicides. However, the herbicides used in the 1960s, 2,4,5-T and 2,4-D, were and other herbicides have since been used with limited success. The spread of the species had been contained by the early 1980s but as seeds are continuously brought in from mature stands inside and outside the park, continuing seedling control is required. At present resources are not available to deal with the large dense stands.
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
C. equisetifolia invades coastal areas of Florida which are free of woody plant species.
Differences in status and ecology between invaded and native ranges 
No obvious differences are apparent, although no diseases have been reported from Florida suggesting that they have little impact on the invading population.
Selected references 
* Little, E.L. & Skolmen R.G. (1989) Common forest trees of Hawaii (native and introduced). Agric. Handbook 679. US Forest Service, Washington.
** LaRosa, A.M., Doren, R.F. & Gunderson, L. (1992) Alien plant management in Everglades National Park: an historical perspective. In Stone, C.P., Smith, C.W. & Tunison, J.T. (Eds) Alien plant invasions in native ecosystems of Hawai'i: management and research, pp. 47‑63. University of Hawaii Press, Honolulu.
*•# Midgley, S.J., Turnbull, J.W. & Johnston, R.D. (Eds) (1983) Casuarina: ecology, management and utilization. CSIRO, Melbourne.
# Pinyopusarerk, K. & House, A.P.N. (1993) Casuarina: an annotated bibliography of C. equisetifolia, C. junghuhniana and C. oligodon. ICRAF, Nairobi.
* Ratnasabapathy, M. (1974) Acacia auriculaeformis and Casuarina equisetifolia ‑ the urban invaders. Malay. Nat. J. 28, 18‑21.
* Vietmeyer, N. (1986) Casuarina: weed or windfall? Am. For. 92(2), 22‑24.
• Troup, R.S. (1921) Silviculture of Indian trees, Vol. 3.
# Wilmot‑Dear, C.M. (1985) Casuarinaceae. In Polhill, R.M. (Ed.) Flora of tropical East Africa. Balkema, Rotterdam.
Pierre Binggeli
May 1997

Cecropia peltata L. (Cecropiaceae)
Short‑lived light demanding tree from tropical America introduced to African and Malaysian botanical gardens or as a shade tree in Ivory Coast. Spreading in disturbed areas, lava flows and forest gaps without displacing native equivalents.

Species characteristics
Life form, size, lifespan
Tree to 20 m high with a lifespan of 20‑30 years. It has large leaves and a small crown. 
Taxonomy, variation and plasticity
The current work on the taxonomy of the genus Cecropia suggest that C. peltata L. (central America), C. pachystachya Trécul (southern America) and C. concolor Willd (Amazon basin) should be regarded as part of the C. peltata complex as they have strong morphological similarities (specimen of unknown origin can not be adequately defined) but have somewhat distinct geographical and/or ecological ranges. Usually evergreen but may be deciduous in areas with a pronounced dry season.
Reproductive biology
C. peltata is dioecious and becomes sexually mature in 3 to 5 years. The minute flowers are clustered on 5 to 10 cm long spikes and are wind‑pollinated. On female individuals the minute one‑seeded fruits form large fruit clusters which appear to take around a month to mature. A spike contains around 800 viable seeds which are about 1.9 mm long and weigh 1.6 mg. In Trinidad bats eat large quantities of the succulent fruits, thus are the main seed disperser although birds also distribute the seeds. In Costa Rica a similar amount of fruits are consumed during the day, mainly by monkeys, and at night by bats and arboreal mammals. A large and persistent seedbank is formed in the forest soil. In Costa Rica flowering and fruiting are seasonal lasting about 9 months with a peak of 4 months during the early part of the wet season. 
Resilience and resistance
In most of its native range C. peltata is inhabited by stinging ants which were thought to protect the tree from herbivory, however in Puerto Rico, where ants are not associated with the species, trees thrive. C. peltata coppices freely following cutting.
Environmental requirements and successional status
Shade intolerant species which dominates early succession. 
Products and uses
The light wood variously used for matchsticks, boxes and crates, interior boarding and paper pulp. Hollow branches and trunks are used to make floats, gutters and trumpets. In places the leaves, latex or bark are employed in medicinal remedies.
Status in native range
Range and abundance
The three sub‑species of the C. peltata complex are distributed as follows: C. peltata in Central America, northern South America and some Caribbean islands, C. pachystachya from central and eastern Brazil to northern Argentina and C. concolor in the Amazon basin. In Puerto Rico C. peltata is one of the most abundant trees. In many parts of its range the species abundance has increased following human related disturbance. In natural forests it is common but patchily distributed.
Climate
Moist tropical and sub‑tropical regions, but is absent from dry coastal and dry limestone areas.
Site requirements 
Regenerates freely as soon as open areas are formed. In natural forests it only becomes established in large gaps and often fails to reach sexual maturity in gaps <150 m2.
Weediness
It is abundant in open areas and in logged and natural forests throughout Puerto Rico and is generally considered to be a weed tree.
Pests and diseases
It is attacked by Historis spp. and various moth species.
Status in invaded regions
History of introductions and intensity of invasions
The tree was introduced to a number of botanical gardens in Cameroon (Limbe formerly Victoria: early 20th century), Zaire (Eala, 1911) and Java (Bogor). In 1953 a trial plot was set up in Malaysia using seeds from Bogor and the species was introduced to Ivory Coast in 1910 as a shade tree in coffee plantations. In 1953 trial plantations were set up in Malaysia. Since the Eala and Bogor material originated from Brazil they would therefore appear to be C. pachystachya, whereas the identity of the Cameroon and Ivory Coast plants is unclear as their origin is unknown. 
Patterns of invasion and time-lag
In the three African regions where C. peltata was introduced, the species has been spreading in disturbed areas in competition with native 'pioneer' species. In Cameroon C. peltata has spread into the gaps of a natural forests where its native equivalent Musanga cecropioides is still 2.5% more common. It has also been recorded as colonizing old lava flows on Mt Cameroon. Along roadsides pure stands may be encountered. In most regions the tree started to spread soon after the introduction. However, in the Ivory Coast the rate of spread was very slow for the first six decades and only after the destruction of most the forest cover did the speed of its spread increase markedly.
Site and climate
Lowland disturbed forests or deforested areas in moist tropical areas. Climate is often seasonal.
Floristic region and vegetation types
Found in a variety of floristic regions.
Pests and diseases
Sometimes the tree is extensively defoliated in Cameroon.
Impact on ecosystem
Competes with or appear to displace native pioneer trees. Impact on vegetation succession unknown.
Impact on humans and related activities
No reports have been made. The tree would probably be regarded as another weedy species without any particularly obnoxious features.
Control
Control of C. peltata has not been reported.
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
In tropical Africa C. peltata appear to be displacing or at least competing with an ecologically equivalent tree Musanga cecropioides R. Br. ex Tedlie. Both trees are taxonomically related and morphologically similar. C. peltata appears to grow faster and is more commonly found on exhausted agricultural soils. Under greenhouse conditions seed germination of the native species is much harder to achieve than that of the exotic. In Malaysia native pioneer species regenerate in smaller forest gaps, produce larger seeds, grow slower in full sunlight and suffer from higher leaf loss rates than C. peltata.
Differences in status and ecology between invaded and native ranges 
No obvious differences between the successional status, habitat requirements or susceptibility to herbivores between the native and invaded regions are noticeable.
Selected references 
* Ake Assi, L. (1979) Cecropia peltata L. (Moracées): ses origines, introduction et expansion dans l'est de la Côte d'Ivoire. In Kunkel, G. (ed.) Taxonomic aspects of African economic botany, pp. 140‑145.
* Bouharmont, J. (1954) Recherches sur les parasoliers congolais (Musanga cecropioides R.Br. et Cecropia leucocoma Miq.). 1. Les conditions favorable à la germination. Agricultura (Louvain) sér. 2, 83‑107.
•• Brokaw, N.V.L. (1998) Cecropia schreberiana in the Luquillo Mountains of Puerto Rico. Bot. Rev. 64, 91‑120.
•• Fleming, T.H. & Williams, C.F. (1990) Phenology, seed dispersal, and recruitment in Cecropia peltata (Moraceae) in Costa Rican tropical dry forest. J. Trop. Ecol. 6, 163‑178. 
* Léonard, J. (1951) Note systématique sur les parasoliers au Congo belge (Musanga et Cecropia ‑ Moracées). Bull. agric. Congo Belge 42, 951‑964.
* McKey, D. (1988) Cecropia peltata, an introduced neotropical pioneer tree, is replacing Musanga cecropioides in south‑western Cameroon. Biotropica 20, 262‑264.
• Putz, F.E. (1983) Treefall pits and mounds, buried seeds, and the importance of soil disturbance to pioneer trees on Barro Colorado Island, Panama. Ecology 64, 1069‑1074. 
* Putz, F.E. & Holbrook, N.M. (1988) Further observations on the dissolution of mutualism between Cecropia and its ants: the Malaysian case. Oikos 53, 121‑125.
#• Silander, S.R. & Lugo, A.E. (1990) Cecropia peltata L. ‑ Yagrumo Hembra, trumpet‑tree. US Dept Agric., Agric. Handb. 654, 244‑249.
* Wetterer, J.K. (1997) Ants on Cecropia in Hawaii. Biotropica 29, 128‑132.
Pierre Binggeli 
September 1999

Chromolaena odorata (L.) King & Robinson (Asteraceae)
Eupatorium odoratum L.
A widely distributed neotropical shrub introduced to many parts of the tropics. Forms pure stands in disturbed areas, grasslands, fallows and forestry plantations. Species spreading rapidly due to its efficient short- and long-distance dispersal abilities.

Species characteristics
Life form, size, lifespan
Multi-stemmed shrub to 2.5 m tall in the open and to 10 m tall when climbing vegetation.
Taxonomy, variation and plasticity
The invasive populations of C. odorata in Asia and southern Africa, both originating from the Caribbean, are morphologically different.
Reproductive biology
Sexual reproduction starts when the plants is one year old. Terminal cymes bear around 70 insect-pollinated flowers. The small fruits (weight: 0.2 mg) mature in about a month. A dense thicket of C. odorata may produce about 109 seeds ha-1 in Ivory Coast and has a very large seedbank. Fruits (cypsella) are typically wind-dispersed as dry and windy weather is necessary for fruit release, however animal dispersal is possible thanks to the fruits small hooks. Flowering initiation appear to be mainly related to the onset of the main dry season and last for three to five months. Seed germination is favoured by water and light and therefore takes place at the start of the rainy season. In India seed dispersal and germination occur before (April-May) and at the start (May-June) of the rains respectively. Active growth takes place through the rainy period until October and is followed by flowering. Seed reach maturity in March.
Resilience and resistance
Shoots may root when touching the ground. It possess an underground 'organ' which ensure the plant's survival in case of fire, drought or mechanical damage through coppicing.
Environmental requirements and successional status
Frost intolerant and is adverse to dry regions. Flourishes in disturbed habitats, particularly in areas of slash an burn agriculture. In Trinidad (native range) on open land C. odorata is a successional species which supersedes the pioneer ephemeral herbs, then is displaced by shrubs and small trees and dies as soon as the forest canopy closes.
Products and uses
Ornamental plant appreciated for its winter flowers. In the West Indies it is known as the 'Christmas bush'. Formerly thought to be useful in controlling coarse grasses, mainly Imperata spp.
Status in native range
Range and abundance
Wide distribution in the neotropics from the USA (29o N) to Argentina (31o S) including most of the West Indian islands.
Climate
Tolerates a variety of temperate and tropical climates. In South America on the western side of the Andes the species does not spread south of 7o S as the conditions are to dry.
Site requirements 
Grows from sea level to 1000 to 2800 m. It occurs on open freely-drained grounds and is absent in natural forests.
Weediness
Site density appears to have increased since last century as a result of human's impact on the environment.
Pests and diseases
Over 240 arthropods have been recorded on C. odorata in Trinidad where the species was investigated in detail for potential biocontrol agents.
Status in invaded regions
History of introductions and intensity of invasions
Introduced to botanical gardens of Dacca (India), Java and Peradeniya (Sri Lanka) in the 19th century and for ornamental reasons in Southern Africa early 20th century. In Western Africa the plant was accidentally introduced with forestry seeds in Nigeria in 1947 and was deliberately introduced to Ivory Coast in 1952 to control Imperata spp. following a recommendations by the famous botanist Auguste Chevalier. In 1994 small infestations of C. odorata were found in Queensland, Australia and it is suspected that the introduction resulted from contaminated pasture seeds from overseas. Introduced and spreading on a number of tropical islands and is also found in a number of temperate regions.
Patterns of invasion and time-lag
In Indian fallows C. odorata recruitment peaks after 3 years and ceases in 10 to 20 years old fallows. Seedling mortality is higher in older fallows and plant vigour decreases after 5 years. Thus the duration of fallows will greatly affect the local abundance of C. odorata. Elsewhere in India in established vegetation C. odorata's survivorship was only 1.4 % in the first year's cohort but much higher in older individuals. Still, despite the high mortality this resulted in a 30% increase in population size in one year. In an Indian monsoon forest C. odorata regenerated freely in selection-felling gaps but was absent from treefall gaps in undisturbed forest. In slash and burn rice cultivation in Ivory Coast forests the fields, if cultivated for only one year, will quickly be filled with pioneer trees after abandonment whereas after 3 years C. odorata will become dominant. Most seed dispersal is local, however, as the seeds have small spines and can cling to fur, feathers and clothes, long distance dispersal is possible. Seeds can also travel great distances with contaminated crop plants or vehicles. In Australia dispersal appear to have also included water, cattle, horses, feral pigs and sugar cane harvesting equipment. No time-lag has been reported.
Site and climate
Distribution limited by rainfall but no absolute minimum exist. The species is generally not present in areas with <1200 mm of rainfall a year and occurs predominantly at altitudes below 1000 m. The species does not appear to have special soil requirements.
Floristic region and vegetation types
Associated with local weeds or secondary vegetation of disturbed areas.
Pests and diseases
In Ivory Coast only insects feed on C. odorata with little impact on the species.
Impact on ecosystem
In Western Africa C. odorata suppresses regeneration of tree species in areas of shifting cultivation if its become well-established. In southern Africa it reduces species diversity and the plants flammability poses a threat to forest edges. 
Impact on humans and related activities
C. odorata is a problem in agricultural land and commercial plantations.
Control
In several tropical countries biological control, using a defoliating artiid, was initiated in the early 1970s generally without success at the exception of Sri Lanka and in the 1980s of Guam. To date only one species has been tried for biological control. An eradication programme has been initiated in Australia using herbicide. 
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
Grows faster than native pioneer species in Ivory Coast.
Differences in status and ecology between invaded and native ranges 
Apart from the apparent higher pest problem in the native range no evidence is available.
Selected references 
* Chandrashekara, U.M. & Ramakrishnan, P.S. (1994) Successional patterns and gap phase dynamics of a humid tropical forest of the Western Ghats of Kerala, India: ground vegetation, biomass, productivity and nutrient cycling. Forest Ecol. Manage. 70, 23‑40.
•• Cruttwell McFadyen, R.E. (1988) Ecology of Chromolaena odorata in the neotropics. In Muniappan, R. (Ed.) Proc. First Int. Workshop on biological control of Chromolaena odorata, pp. 13‑20. Bangkok.
** Cruttwell McFadyen, R.E. & Skarrat, B. (1996) Potential distribution of Chromolaena odorata (siam weed) in Australia, Africa and Oceania. Agric. Ecosyst. Environ. 59, 89‑96.
** Gautier, L. (1992) Taxonomy and distribution of a tropical weed: Chromolaena odorata (L.) R. King & H. Robinson. Candollea 47, 645‑662. 
*• Gautier, L. (1993) Reproduction of pantropical weed: Chromolaena odorata (L.) R. King & H. Robinson. Candollea 48, 179‑193.
* Ivens, G.W. (1974) The problem of Eupatorium odoratum L. in Nigeria. PANS 20, 76‑82.
* Kushwaha, S.P.S., Ramakrishnan, P.S. & Tripathi, R.S. (1981) Population dynamics of Eupatorium odoratum in successional environments following slash and burn agriculture. J. appl. Ecol. 18, 529‑535.
** Rouw, A. de (1991) The invasion of Chromolaena odorata (L.) King & Robinson (ex Eupatorium odoratum), and competition with the native flora, in a rain forest zone, south‑west Cote d'Ivoire. J. Biogeogr. 18, 13‑23.
* Yadav, A.S. & Tripathi, R.S. (1981) Population dynamics of the ruderal weed Eupatorium odoratum and its natural regulation. Oikos 36, 355‑361.
Pierre Binggeli 
May 1997

Clidemia hirta (L.) D. Don (Melastomataceae)
Neotropical bird-dispersed shrub introduced to many parts of the tropics. Considered a weed on many oceanic islands where it forms dense thickets and suppresses most ground vegetation. Even small stands are impossible to eradicate.

Species characteristics
Life form, size, lifespan
Densely-branched shrub up to 5 m tall but normally between 0.5 and 3 m.
Taxonomy, variation and plasticity
A taxonomically difficult genus and the plant has sometimes been misidentified. Varieties of C. hirta have been described. Var. hirta and var. elegans were introduced to Hawai'i and the Seychelles respectively.
Reproductive biology
Several white or pinkish flowers borne on axillary or terminal cymes. A mature plant can produce over 500 blue-black berries (6-9 mm long) per year each containing over 100 seeds (0.5-0.75 mm long). Seeds form a very large seedbank where they remain viable for up to 4 years. In Hawai'i, long distance dispersal is carried out by humans and seeds are locally-disseminated by birds and feral pigs which can also carry seeds in their fur. In Hawai'i flowering and fruiting occurs all year round where there is no dry season and rainfall exceeds 2500 mm.yr-1. In areas where a dry season occur flowering ceases.
Resilience and resistance
In windy areas the shrub is scrambling and is less than 1 m tall. Resistant to drought lasting up to 6 months although some shoot tips die back during the dry season. It does not appear to tolerate salt-spray. On the ground of rain forests detached leaves can root.
Environmental requirements and successional status
In the native range it is an early coloniser of disturbed areas and is rapidly replaced by vines. Tolerates full sun light as well as complete canopy cover.
Products and uses
Has no fodder value and no known uses. 
Status in native range
Range and abundance
Widely distributed in Central and South America and the Caribbean islands where it is not a very common plant.
Climate
Broad climatic requirements ranging from dry to wet tropics.
Site requirements 
It is an early colonizer of open areas, including slash-and-burn agricultural grounds, where it becomes dominant twelve months after disturbance before being smothered by vines. It is found in low densities in open forested areas, forest plantations, and roadsides. In Jamaica its altitudinal distribution ranges between 30 and 1200 m a.s.l.
Weediness
Not weedy but said to be common in Jamaica in moist pastures.
Pests and diseases
All plants show signs of heavy herbivory.
Status in invaded regions
History of introductions and intensity of invasions
C. hirta is a serious weed on many tropical oceanic islands (e.g. Fiji, Seychelles), southeast Asia, India and East Africa. The date of introduction to Hawaiian Islands is unknown and it was first recorded in 1941. It was grown in the Wahiawa Botanic Garden and was thought to be "very promising because it won't be spread by birds". It was first noted as escaping in 1949 on the island of O'ahu and by 1952 covered at least 100 ha. By the late 1990s it had invaded all suitable habitats covering over 100,000 ha. In the 1970s and 1980s it was accidentally introduced by humans to five other Hawaiian islands. On Fiji C. hirta was probably accidentally introduced prior to 1890 with coffee plants imported from British Guiana. It became a pest by 1920.
Patterns of invasion and time-lag
In Hawai'i all new spread occurs in disturbed areas such as roadsides and landslides and following disturbance by windstorm, pigs and fire. If seeds are present they germinate rapidly and within two years the disturbed area can become smothered. However, on the steep slopes of the Seychelles enough light reaches the ground for C. hirta regeneration to take place without forest canopy disturbance. Although this species is rarely recorded until it forms monotypic stands, the more recent Hawaiian introductions suggest that it starts to spread as soon as it is introduced to new suitable habitats subjected to regular disturbance.
Site and climate
C. hirta tolerates widely differing tropical climatic conditions including a wide range of rainfall (<1000 to > 2500 mm). On the Seychelles the shrub is absent from drier areas.
Floristic region and vegetation types
Most tropical island forest areas appear to be susceptible to C. hirta invasion regardless of their floristic composition as long as some form of disturbance affects them.
Pests and diseases
It is only affected by one insect introduced as a biocontrol agent.
Impact on ecosystem
Under heavy infestations of C. hirta most plant, including most mosses and liverworts normally found in shaded habitats and subcanopy species, are displaced. It is thought that the species has the potential of driving some species to extinction.
Impact on humans and related activities
In Hawai'i the plant is despised because of its dense growth. Its growth along trails and roadsides increases maintenance costs as well as reduce the aesthetic, educational and recreational value of forest lands. In Fiji it renders large areas of grazing land useless and interferes with the development of plantations (rubber, cocoa).
Control
Biological control, using the thrips Liothrips urichi, was initiated in Fiji in the early 1930s and much later in Hawai'i. The introduced insect seriously affect the growth of C. hirta in open sunny areas whereas in shaded areas (forest or frequent cloud cover) it is not effective. The only hope of controlling an invading population of C. hirta is to identify the problem at a very early stage and eradicate all seed-sources. In Hawai'i repeated efforts to control seedlings in expanding populations have failed.
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
No ecological equivalent appears to exist.
Differences in status and ecology between invaded and native ranges 
C. hirta suffers from heavier insect herbivory and subjected to strong competition from other Melastomataceae and vines in its native range. In the native range the species is purely an early successional species whereas in parts of its invaded range it can become established below forest canopy. In Hawai'i the shrub grows taller.
Selected references 
* Gerlach, J. (1993) Invasive melastomataceae in Seychelles. Oryx 27, 23‑26.
• Gleason, H.A. (1939) The genus Clidemia in Mexico and Central America. Brittonia 3, 97‑140.
* Markin, G.P., Lai, P.‑Y. & Funasaki, G.Y. (1992) Status of biological control of weeds in Hawai'i and implications for managing native ecosystems. In Stone, C.P., Smith, C.W. & Tunison, J.T. (Eds) Alien plant invasions in native ecosystems of Hawai'i: management and research, pp. 466‑482. University of Hawaii Press, Honolulu. 
** Nakahara, L.M., Burkhart, R.M. & Funasaki, G.Y. (1992) Review and status of biological control of clidemia in Hawai'i. In Stone, C.P., Smith, C.W. & Tunison, J.T. (Eds) Alien plant invasions in native ecosystems of Hawai'i: management and research, pp. 452‑465. University of Hawaii Press, Honolulu.
* Sheil, D. (1994) Naturalized and invasive plants in the evergreen forests of the East Usambara Mountains, Tanzania. Afr. J. Ecol. 32, 66‑71. 
**Smith, C.W. (1992) Distribution, status, phenology, rate of spread, and  management of Clidemia in Hawai'i. In Stone, C.P., Smith, C.W. &  Tunison, J.T. (Eds) Alien plant invasions in native ecosystems of  Hawai'i: management and research, pp. 241‑253. University of Hawaii  Press, Honolulu.
* Wee, Y.C. & Corlett, R. (1986) The city and the forest. Singapore University Press, Singapore. 
** Wester, L.L. & Wood, H.B. (1977) Koster's curse (Clidemia hirta), a weed pest in Hawaiian forests. Environ. Conserv. 4, 35‑41.
Pierre Binggeli 
May 1997

Lantana camara L. (Verbenaceae)
Variable shrub native to tropical America introduced to most of the tropical and sub-tropical regions. Forms extensive impenetrable thickets in disturbed areas but is also found in the understorey of open forests. 

Species characteristics
Life form, size, lifespan
Two to five meter tall shrub. Erect in the open and scrambling in scrubland.
Taxonomy, variation and plasticity
L. camara is a highly variable species. It has been cultivated for over 300 years and now has hundred of cultivars and hybrids. These belong mostly to the Lantana camara complex. Cultivars can be distinguished morphologically (variation in: flower size, shape and colour; leaf size, hairiness and colour; stem thorniness), physiologically (variation in: growth rates, toxicity to livestock) and by their chromosome number and DNA content.
Reproductive biology
Flowers are yellow, later turning orange then red and remain on the axillary inflorescence for three days. The flowers, when yellow, produce nectar and are pollinated by butterflies. The species is an obligate outcrosser. It is unclear whether apomixis occur. The fleshy drupe is 3-6 mm in diameter containing 1-2 seeds (1.5 mm long). Fruits mature rapidly and change colour from dark green to black. A number of bird species and sometimes sheep and goats disperse the seeds. Flowering and fruiting throughout the year with a peak during the first two months of the rainy season. Heavy fruit production produced yearly.
Resilience and resistance
The alkaloid rich leaves are virtually immune to herbivory. It can spread vegetatively. Stems and roots coppice freely following herbicidal treatment. Slashing and burning stimulate suckering. Allelopathic effect induced by L. camara inhibits growth of other vegetation as well as seed germination. It has low tolerance for boggy soils, saline soils and is susceptible to frost.
Environmental requirements and successional status
Thrives in open and disturbed areas as well as in open natural vegetation. Being somewhat shade-tolerant and it can become the dominant understorey shrub in open forests.
Products and uses
Ornamental plant which was often used for hedges and erosion control. Twigs are used as fuel. A number of minor uses include seeds as lamb food, biogas production when its straw is mixed with dung, and medicinal purposes.
Status in native range
Range and abundance
Native to Central and South America. Original distribution unclear due to the introduction of a number of ornamental varieties. Species poorly investigated.
Climate
Site requirements 
In the West Indies it is found in dry thickets.
Weediness
In Central America L. camara is a weed in a number of crops and is common in pastures, waste areas and roadsides.
Pests and diseases
Many insect species attack flowers, flower stalks, leaves, stems, shoots and roots. Their impact on shrub vigour and seed set is not known.
Status in invaded regions
History of introductions and intensity of invasions
L. camara has been introduced throughout the tropics and subtropics as an ornamental, often used as a hedge plant. It is regarded as a cosmopolitan weed and in many countries it has been declared a noxious weed. Mostly introduced during the late 19th century but a number of cultivars and forms were subsequently introduced.
Patterns of invasion and time-lag
L. camara forms extensive, dense and impenetrable thickets in forestry plantations, orchards, pasture land, waste land and in natural areas. The rapid spread of L. camara is associated with human induced disturbance. Fruits are widely dispersed by many birds including introduced species. On the Galapagos L. camara started to spread soon after its introduction. In scrub areas of New Caledonia the plant scrambles through the vegetation not unlike climbers. However in taller forests it is absent and is rarely found in large treefall gaps. In areas where natural fires occur they stimulate thicker regrowth.
Site and climate
Tolerates a wide range of climates. In Australia L. camara tolerates a mean annual rainfall from 4000 mm to less than 1000 mm. Found between sea level and nearly 1000 m on Hawaii and higher in East Africa. Its distribution is affected by soil type, but grows well on poor soils. 
Floristic region and vegetation types
A wide array of regions and vegetation types at the exception of closed forests and wet communities.
Pests and diseases
No reports of important pests and diseases.
Impact on ecosystem
The spread of L. camara on the Galapagos islands is seen as a threat to bird breeding populations and plant communities containing rare endemics. Its extensive seed production favours rat populations. In New Caledonia, by increasing fire intensity as a result of its large dry biomass as well as its smothering effect, it displaces natural scrub communities.
Impact on humans and related activities
L. camara poisoning in cattle and sheep have often been recorded. Children have died after eating unripe berries. The dense thickets, particularly those of the thorny variety, deter human access. In forestry it tends to over-run young plantations and prevents access to older plantations. In Indian sandalwood forests the shrub competes with the tree crop as well as favours the spread of the sandal spike disease. In some mountainous areas (Tanzania, India) the presence of L. camara was once considered as a good erosion preventing ground cover. It encroaches agricultural land, reduces the carrying capacity of pastures and is a weed in many agricultural crops. In New Caledonia following reproduction the climbing stems dry out and the dead material falls to the ground increasing fire susceptibility. In Tanzania L. camara can be considered as a serious health threat, as its thickets provide breeding grounds for Tsetse flies infected with trypanosomes of domestic animals. 
Control
Since the turn of the century, biological control has been attempted in many parts of the tropics with varying degrees of success as different cultivars display differences in susceptibility to insect herbivores. Greater success appears to have been achieved in drier areas. In Uganda the introduction of Teleonemia scrupulosa Stal, used harmlessly in Australia and Fiji, was less successful as it attacked the crop Sesamum indicum L. Chemical control is expensive and cleared areas are rapidly reinfected by seedlings and stem and roots freely coppice. Mechanical control can be effective , particularly where land is cleared, but is labour intensive and requires continual follow-up treatment to remove roots and seedlings.
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
Differs from native plants by a combination of fast growth rates, allelopathy, fire tolerance, and great variability (i.e. numerous cultivars).
Differences in status and ecology between invaded and native ranges 
There are no indications that any major differences exist between the invaded and native ranges.
Selected references 
** Davis, C.J., Yoshioka, E. & Kageler, D. (1992) Biological control of lantana, prickly pear, and Hamakua pamakani in Hawai'i: a review and update. In Stone, C.P., Smith, C.W. & Tunison, J.T. (Eds) Alien plant invasions in native ecosystems of Hawai'i: management and research, pp. 411‑431. University of Hawaii Press, Honolulu.
** Fensham, R.J., Fairfax, R.J. & Cannell, R.J. (1994) The invasion of Lantana camara L. in Forty Mile Scrub National Park, north Queensland. Aust. J. Ecol. 19, 297‑305.
*• Morton, J.F. (1994) Lantana, or red sage (Lantana camara L., [Verbenaceae]), notorious weed and popular garden flower; some cases of poisoning in Florida. Econ. Bot. 48, 259-270.
• Schemske, D.W. (1983) Lantana camara (Cinco Negritos, Lantana). In Janzen, D.H. (Ed.) Costa Rican natural history, pp. 266‑268. The University of Chicago Press, Chicago.
** Sharma, O.P., Makkar, H.P.S. & Dawra, R.K. (1988) A review of the noxious plant Lantana camara. Toxicon 26, 975‑987. 
*• Sinha, S. & Sharma, A. (1984) Lantana camara L. ‑ a review. Feddes Repert. 95, 621‑633. 
** Swarbrick, J.T. (1986) History of lantanas in Australia and origins of the weedy biotypes. Pl. Prot. Quart. 1, 115‑121. 
** Thaman, R.R. (1974) Lantana camara: Its introduction, dispersal and impact on islands of the tropical Pacific Ocean. Micronesica 10, 17‑39. 
• Winder, J.A. (1980) Factors affecting the growth of Lantana in Brazil. Ph.D. thesis, University of Reading.
Pierre Binggeli
October 1999

Leucaena leucocephala (Lam.) De Wit (Mimosaceae)
L. glauca (Willd.) Benth.
A widely planted multipurpose tree from tropical America introduced to most of the tropics. Forms monotypic stands in dry lowland areas of oceanic islands and regenerate freely in most of the tropics. 

Species characteristics
Life form, size, lifespan
Deciduous tree usually growing to 9 m and in places up to 18 m high.
Taxonomy, variation and plasticity
Two subspecies of L. leucocephala, leucocephala and glabrata, are recognized. The former is shrubby. The species is evergreen when moisture is not limiting.
Reproductive biology
Globular flower heads contain numerous tiny hermaphrodite white flowers. Largely self-fertilised and self-compatible but hybridization with other species of the genus occurs readily. The 18 cm long pods contain about 20 seeds (size: ca 7 x 3 mm) and are borne in clusters of around 20. Germination rates vary from 5% to 90%. Flowering starts within a year of germination and after two years trees produce fruits all year round. Flowering increases under moisture stress or with the onset of shorter days in the sub-tropics. In India there are two flowering and fruiting seasons with a period of around four months separating flowering from pod dehiscence.
Resilience and resistance
Leaves are shed as a result of light frosts and after a heavy frost all above ground growth will die but the crown will survive and sprout vigorously the following year. Some Mexican provenances appear to be more frost tolerant. Stem and crown cuttings root and tree coppices well when cut and after fire. This very deep-rooted species fixes nitrogen and is drought tolerant even at the young seedling stage.
Environmental requirements and successional status
L. leucocephala has moderate tolerance for shade as it can regenerate under its own canopy and under Lantana camara.
Products and uses
It is used as a shade plant in coffee, rubber, cacao and cinchona plantations, for reforestation, windbreaks and firebreaks. Necklaces are made with the seeds.
Status in native range
Range and abundance
The extent of its range is uncertain but it is native to Mexico and probably to Central America and West Indies. The origin of this tetraploid species is unknown.
Climate
The climate is seasonal with a 3-6 month dry season and a rainfall of 750-1800 mm. The altitudinal range is the main difference between subspecies leucocephala and glabrata. They grow from sea level to, respectively, 500 and 1500 m.
Site requirements 
It forms thickets in dry limestone and dry coastal regions of Puerto Rico.
Weediness
In Puerto Rico commonly found along roadsides and abandoned pasture.
Pests and diseases
Several pests and diseases affect L. leucocephala including a leaf spot disease Camptomeris leucaenae.
Status in invaded regions
History of introductions and intensity of invasions
Extensively planted worldwide and presently covering up to 5 million ha. Until the end of the 19th century all introductions were of the shrubby type but subpecies glabrata has been widely introduced over the past three decades. Introduced to the Pacific islands by the Spanish who over 400 years ago transported L. leucocephala feed and seeds to the Philippines. Introduced to Hawaii in 1864 and to the Marquesas Islands prior to 1893. It is now common in the lowlands of many Pacific islands often forming monotypic stands. In India it is thought to be a weed with tremendous natural regeneration. 
Patterns of invasion and time-lag
L. leucocephala invades cleared areas and forms dense thickets. In the Hawaiian islands it sometimes becomes the dominant part of the vegetation at low altitude (0 - 300 m) on dry and disturbed sites. In the Marquesas Islands the tree is spreading into native disturbed forest. Plant growth is very variable. In poor conditions it is vulnerable to weed competition and wildlife. In India the tree spread into fallows within a few years of planting although no regeneration was recorded beyond a distance of 40 m. The species was reported to be abundant soon after its introduction to Hawai'i. During the 1980s crown dieback observed in many parts of Hawai'i it appears that trees with an understorey of shallow rooted naturalised succulents suffered from less dieback and were more vigorous than with a grassy understorey. The differing water requirements between the succulents and the grasses may explain these observations. 
Site and climate
In Hawai'i it is naturalised at sites which receive only 300 mm rain per year. Under cultivation it performs well in regions with a mean annual rainfall ranging from 650 to 3000 mm. Grows on a wide variety of soils.
Floristic region and vegetation types
Lowland vegetation on many Pacific Islands is now almost entirely dominated by introduced species. On the Marquesas Islands the dry lowland forests contain 28 woody species of which 9 are aliens. The lowland vegetation of Hawai'i has been much altered and is now dominated by exotics.
Pests and diseases
In Hawai'i an introduced beetle larvae destroys seeds and nearly all pods are infested. Since 1983, the psyllid Heteropsylla cubana from Cuba has been rapidly spreading westward throughout the Pacific and tropical Asia. Particularly in dry regions it results in total defoliation, death of terminal shoots and inhibits flowering, and repeated attacks result in tree death.
Impact on ecosystem
Although the impact of L. leucocephala on the invaded ecosystem has not been reported in much detail, it is clear that the tree, as well as other introduced species, displaces the native lowland vegetation of Pacific islands. Under a L. leucocephala canopy, which is relatively open, the soil is often free of vegetation.
Impact on humans and related activities
Once considered as the 'miracle tree' because of the variety of uses, including, firewood, timber, human food, green manure, shade, erosion control and forage. However both the foliage, high in protein and vitamin A, and the edible seeds contain the toxic amino acid mimosine and therefore can be toxic in large quantities. Horses, feeding on the tree, lose their hairs. In the Marquesas Islands farmers consider the species as an agricultural weed which is nearly impossible to uproot completely. 
Control
A clear conflict of interest between the agroforestry value of the tree and its deleterious environmental impact can be seen in the practitioners attitude towards the psyllid Heteropsylla cubana. Agroforestry has suffered from serious economic losses, in Java estimated at $ 2.8 million between 1986 and 1988 as a result of the pest and biological control programme of the insect have been initiated. On the other hand managers of some Pacific islands, where L. leucocephala is considered a weed, would consider the arrival of the psyllid as beneficial. In western Africa the tree grows freely both from seed and cuttings, the plant becomes a pest difficult to eradicate from cultivated land.
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
L. leucocephala and other woody invaders of lowland dry vegetation of oceanic islands probably have some, as yet undetermined, competitive advantage over native species and/or native species lack the characteristics necessary to cope with high levels of human disturbance.
Differences in status and ecology between invaded and native ranges 
No differences have been reported.
Selected references 
* Hallé, F. (1978) Arbres et forêts des Iles Marquises. Cahiers du Pacifique 21, 315‑357. 
*#• Hughes, C.E. (1993) Leucaena genetic resources. Oxford Forestry Institute, Oxford.
* Ikagawa, T. (1988) Leucaena dieback and the cereus cacti in Hawaii: an observed positive relationship between naturalized introduced species. Leucaena Res. Reports 9, 123-126.
# Lenné, J.M. (1991) Diseases of Leucaena species. Trop. Pest Mgmt 37, 281-289.
•• Little, E.L. & Wadsworth, F.H. (1964) Common trees of Puerto Rico and the Virgin Is. Agric. Handb. No. 249. USDA Forest Service, Washington.
* Patil, M.S. & Kumar, H.D.M. (1990) Seed dispersion in subabul ‑ a case study. Ind. Forester 116, 598‑599.
# Shelton, H.M. & Brewbaker, J.L. (1994) Leucaena leucocephala ‑ the most widely used forage tree legume. In Gutteridge, R.C. & Shelton, H.M. (Eds) Forage trees as legumes in tropical agriculture, pp. 15‑29. CAB International, Wallingford.
# Vandeschricke, F., Quilici, S., Gauvin, J. & Roederer, Y. (1992) Le psylle du leucaena à la Réunion: importance des dégats et perspectives de lutte biologique. Bois For. Trop. 234, 47‑59.
Pierre Binggeli 
May 1997

Maesopsis eminii Engler (Rhamnaceae)
A large African tropical forest tree introduced to various parts of the tropics for timber production or as a shade tree. Naturally regenerating in many places and invasive in the rain forests of the East Usambaras (Tanzania).

Species characteristics
Life form, size and lifespan
Large canopy tree reaching a height of up to 43 m and a diameter of 1.2 m. Exceptionally able to live up to 200 years.
Taxonomy, variation and plasticity
The genus Maesopsis is monospecific. On the basis of height and wood quality variation a western African sub-species (M. eminii subsp. berchemoides Hallé) has sometimes been recognized. Tree height increases from about 15 m in western Africa to over 40 m in East Africa. The size and the dentation of the entire leaf exhibit much variation. The species is either deciduous or semi-deciduous depending on local climatic conditions.
Reproductive biology
The sex expression and pollination system is poorly understood but flowers are thought to be hermaphrodite and protogynous and insects are the likely pollinating agent. Flowering and fruiting starts after four to ten years and large seed crops are produced every year often every six months. A number of birds, including hornbills, and monkeys dispersed the large drupe (2-3 cm). Seeds remain dormant for up to at least 200 days. Germination is not triggered by light but appears to be affected by lunar cycles and enhanced soil humidity promotes early germination.
Resilience and resistance
Coppices freely after being cut and is susceptible to fire.
Environmental requirements and successional status
Usually described as a pioneer M. eminii germinate and seedlings survive under forest canopy for a few months. However, to grow and reach canopy height M. eminii requires large canopy gaps. At the forest-savanna boundary it becomes established under shrubby vegetation.
Products and uses
Timber is soft but firm and strong, and widely used in Uganda. However, the wood is not resistant to termites and fungal decay. M. eminii has been used in eastern Tanzania and Fiji in forestry plantation. It is used in India as a shade tree in coffee plantations and elsewhere in Asia as an agroforestry tree.
Status in native range
Range and abundance
M. eminii is widely distributed throughout moist tropical Africa from Liberia to Uganda and south to Angola. Usually an uncommon tree with the exception of the forest-savanna boundary in Uganda where it may be dominant. 
Climate
Broad spectrum of climate requirements from per-humid tropics to seasonal tropics.
Site requirements 
In moist forests M. eminii becomes established in large forest gaps. In Uganda, it does not regenerate in grassland mainly because of its susceptibility to fire. At these sites the grassland must be colonised by fire resistant species before M. eminii regenerates to form dominant stands. Subsequently succession proceeds to a high forest containing only a small proportion of M. eminii. On Lake Victoria islands succession from grassland to forest is similar except that it normally takes place around anthills. This suggests that higher nutrient status is necessary for tree colonisation to occur.
Weediness
In most of its native range M. eminii has no weedy tendencies, on the contrary it is usually scarce even in secondary forests.
Pests and diseases
Many insects and fungal diseases affect M. eminii causing defoliation, stem breakages and bark cankers.
Status in invaded regions
History of introductions and intensity of invasions 
Introduced, probably from the Bukoba regions in western Tanzania, to the Amani Botanic Gardens in the East Usambara (eastern Tanzania) in 1913 when a 1 ha forestry trial plot was set up. Large-scale forestry planting was undertaken during the 1960s and early 1970s. M. eminii is now dominant in secondary forests near the M. eminii plantation and is found in many natural forest treefall gaps.
Natural regeneration and spread observed in Rwanda, Fiji, India and on Pemba Island (Tanzania). In Puerto Rico it regenerates profusely and is likely to become common or abundant in forests within the next century.
Patterns of invasion and time-lag
In the natural forest in the East Usambaras M. eminii becomes established in large treefall gaps and pit-sawing gaps where light levels are high. Seedling establishment occurs on bare humus soil. Less than 15 years lapsed between the introduction of M. eminii until it was first reported as regenerating in the natural forest.
Site and climate
Mountainous area at an altitude of ca. 1000 m. The climate is seasonal and frost-free with two rainy seasons and the annual rainfall varies between 1,000 mm and 2,000 mm.
Floristic region and vegetation types
The East Usambaras are part of the isolated Eastern Arc Mountains of Eastern Africa. Their sub-montane forests contain a number of endemic or near endemic species and have a high conservation value.
Pests and diseases
Little damage occur apart from limited fungal attack on young seedlings and some squirrel seed predation.
Impact on ecosystem
M. eminii becomes dominant in logged forests and regenerates in treefall gaps. It alters soil properties and associated fauna. Impact on tree regeneration probable but evidence inconclusive. 
Impact on humans and related activities
In the East Usambaras people have no use for the wood, including as firewood, and do not exploit it. Farmers or foresters do not consider M. eminii as a pest as the tree does not have thorns or any other obvious negative effects on human activities.
Control
As yet no control programme has been initiated. Since the tree coppices readily, felling stands dominated by M. eminii must be accompanied with bark removal of stumps. Ring barking does not lead to crown death unless the cambium and part of the xylem are cut. Trees may be killed using arboricide.
Ecological differences
Existence of ecological equivalent species and competitive interactions in invaded regions
In the East Usambaras no equivalent species exist. A combination of very fast growth rates (in full light), large bird-dispersed fruits and seeds, short-term (few months) shade-tolerance in newly germinated seedlings and shade intolerance thereafter are a unique combination of characteristics in M. eminii.
Differences in status and ecology between invaded and native ranges 
In the East Usambaras M. eminii does not appear to suffer from any significant attacks from pests and diseases similar to those reported from Uganda. Regeneration in treefall gaps, common in the East Usambaras, is scarce in the native range. M. eminii dominance in secondary vegetation is never observed in native range.
Selected references 
* Beentje, H.J. (1990) Botanical assessment of Ngezi Forest, Pemba Island, Zanzibar. Zanzibar Forestry Devl. Plan, Finnida, Zanzibar.
** Binggeli, P. (1989) The ecology of M. eminii invasion and dynamics of the evergreen forest of the East Usambaras, and their implications for forest conservation and forestry practices. In Hamilton, A.C. & Bensted‑Smith, R. (Eds) Forest conservation in the East Usambara Mountains, Tanzania, pp. 269‑300. IUCN, Gland.
** Binggeli, P. & Hamilton, A.C. (1993) Biological invasion by Maesopsis eminii in the East Usambara forests, Tanzania. Opera Bot. 121, 229‑235.
•• Eggeling, W.J. (1947) Observations on the ecology of the Budongo rain forest, Uganda. J. Ecol. 34, 20‑87. 
* Hall, J.B. (1995) Maesopsis eminii and its status in the East Usambara Mountains. East Usambara Catchment Forest Project Technical Paper No. 13. Finish Forest & Park Service, Vantaa.
# Johnston, M.C. (1972) Rhamnaceae. In Milne‑Readhead, E. & Polhill, R.M. (Eds) Flora of tropical Africa. Crown Agent for Overseas Government & Administration, London. 
# Normand, D. (1935) Sur le Maesopsis de l'ouest africain et la bois de nkanguele. Rev. bot. appl. Agric. trop. 15: 164, 252‑263. 
* Sreenivasan, M.S. & Dharmaraj, P.S. (1991) Maesopsis eminii Engl ‑ a fast growing shade tree for coffee. Indian Coffee 55, 17‑20. 
• Thomas, A.S. (1941) The vegetation of the Sesse Islands, Uganda. An illustration of edaphic factors in tropical ecology. J. Ecol. 29, 330‑353.
Pierre Binggeli
May 1997

Melaleuca quinquenervia (Cav.) S.T. Blake (Myrtaceae)
Australasian tree forming large monospecific stands in swampy areas of southern Florida. The tree is compressing the distribution of a poorly-adapted swamp tree to wetter areas.

Species characteristics
Life form, size, lifespan
Evergreen tree to 20-25 m tall. 
Taxonomy, variation and plasticity
M. quinquenervia is one of a group of several closely related species. It has frequently been confused with M. viridiflora and intermediates between the two have been reported.
Reproductive biology
The tree reaches sexual maturity within two years. Spikes bear white malodorous flowers with large stamens. The flowers produce large quantities of pollen and nectar and are pollinated by bees. The fruit is a woody capsule (4 mm) containing many minute seeds (<1.5 mm, 30,000 seeds g-1). Seeds have no special buoyancy structures and are usually poorly dispersed but in hurricane winds seeds can spread up to 7 km. Seeds may be retained in the seed capsule for several years, with up to 20 million seeds stored per tree. They are generally released when flow of moisture from the tree to the capsule is interrupted by the death of the branch usually as a result of fire or frost. However, some continuous seedfall has been observed with seasonal peaks. In Florida 10-20% of released seeds germinate. Seedlings grow up to 2 m per year.
Resilience and resistance
Resistant to wind, drought, fires and salt water. It has only slight resistance to frost although rootstock survives and sprouts. Coppices from cut stumps. The thick spongy bark of the trunk is fire proof but the outer layer highly flammable. The leaves and branches are killed during fires but are rapidly replaced by sprouts. Under flooded conditions fibrous roots are formed at the base of the trunk.
Environmental requirements and successional status
Species becomes locally dominant in swampy areas over a wide geographical area. It successfully competes with and outgrows other vegetation.
Products and uses
The wood is used for a number of purposes in Australia. It is suitable for windbreaks and beach planting. The papery bark is used as fruit packing material and torches.
Status in native range
Range and abundance
Native to eastern Australia, Papua New Guinea and Irian Jaya and often forms pure stands. It is relatively common throughout its range. Formerly thought to occur in New Caledonia, where the tree is now considered to be a distinct species.
Climate
Grows at an altitude of 5 - 100 m. It has broad mean annual temperature (18C to 34C) and rainfall (1000 mm to 5000 mm) requirements. Climate is monsoonal in the tropical part of its distribution.
Site requirements 
In Australia the tree is sometimes considered to be fire intolerant and natural stands, which are often pure, are confined to wetlands. It occurs most frequently on peaty humic gleys, sandy at the surface but with silt or clay below and with a high organic component. 
Weediness
Not reported in Australia.
Pests and diseases
In Australia insects significantly reduce girth, height and biomass increment in saplings.
Status in invaded regions
History of introductions and intensity of invasions
Introduced to Florida as an ornamental in 1906 in at least two coastal locations. Seeding from airplanes was carried out in the 1930s and in the 1940s trees were planted inland. In Hawai'i over 1.7 million trees have been planted in forestry plots and species is now naturalized in undisturbed mesic forest (altitude 30-890 m). First cultivated in 1920 using seeds from Florida.
Patterns of invasion and time-lag
The seasonal water regime and frequency of fire are the major factors determining the suitability of sites for M. quinquenervia establishment. The rate of spread of the tree increased dramatically with increased fire regime and the creation of new invasion foci resulting from natural seed dispersal. For many years M. quinquenervia caused no problems in Florida. 
Site and climate
Southern Florida consists of a large swampy lowland region where slight changes in elevation alter the water regime which affects drainage, fire and salinity. The climate is sub-tropical with an annual rainfall of 1600 mm falling mostly between May and October. Occasional frosts occur.
Floristic region and vegetation types
The slight difference in elevation and associated variation in water regime result in a number of vegetation types including mangroves, marshes and forests. The Florida vegetation is isolated from other sub-tropical regions of northern America and is rich in endemics but prone to invasions.
Pests and diseases
Free from insect herbivory.
Impact on ecosystem
M. quinquenervia displaces native vegetation particularly Taxodium distichum var. nutans, a temperate tree at the limit of its range. Its dense canopy casts deep shade, and in association with its likely allelopathic properties, restricts ground vegetation. It is poorly utilized by wildlife. By increasing the forest cover it could result in higher demand for ground water and lowering of the water-table. 
Impact on humans and related activities
Was considered to be a worthwhile and beneficial plant prior to its spread. Presently has no commercial uses but could be used for cellulose or as a fuel. As a nectar and pollen source it is important to the beekeeping industry. It appears to be a respiratory irritant when found close to human habitations and seems to repel mosquitos.
Control
In Florida current management programmes include a mixture of manual, mechanical and herbicidal control. Biological control is under study and a number of insect species are being evaluated in Australia. Since fire frequency is determined by water regime and water regime can be altered in large areas of southern Florida, water management is a possible means of limiting the spread.
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
M. quinquenervia becomes dominant on the ecotone between dry pine forests and swamp forest where the conditions are either too wet for pine or too dry for Taxodium distichum var. nutans. There appear to be few fire-tolerant tree species particularly suited to the south Florida environment, including T. distichum which phenology is out of phase with the local environment.
Differences in status and ecology between invaded and native ranges 
It has been suggested that in Florida trees are quite different in appearance from those observed in Australia. They are generally taller, straighter and form very dense populations and grow much faster. This appears to result from the absence of herbivory. Differences in fire tolerance between Florida and Australia may also be attributable to differences in herbivory. Climatic conditions in Florida and in New South Wales, where the seed source originated, are similar. 
Selected references 
• Balciunas, J.K. & Burrows, D.W. (1993) The rapid suppression of the growth of Melaleuca quinquenervia saplings in Australia by insects. J. Aquat. Pl. Mgmt 31, 265‑270. 
#• Cherrier, J.F. (1981) Le niaouli en Nouvelle-Calédonie (Melaleuca quinquenervia S.T. Blake). Rev. for. fr. 33, 297-311.
#• Doran, J.C. & Turnbull, J.W. (in press) Melaleuca quinquenervia (Cav.) S.T. Blake. In Ibrahim, F.H. & Maesen, L.J.G. van (Eds) Auxillary plants in agriculture and forestry. Prosea, Wageningen.
* Geiger, R.K. (Ed.) (1981) Proceedings of Melaleuca Symposium, Sept. 23‑24, 1980. Florida Division of Forestry.
** Laroche, F.B. & Ferriter, A.P. (1992) The rate of expansion of Melaleuca in South Florida. J. Aquatic Pl. Mgmt 30, 62‑65.
# Morton, J.F. (1966) The cajeput tree ‑ a boon and an affliction. Econ. Bot. 20, 31‑39.
** Myers, R.L. (1983) Site susceptibility to invasion by the exotic tree Melaleuca quinquenervia in southern Florida. J. appl. Ecol. 20, 645‑658.
** Myers, R.L. (1984) Ecological compression of Taxodium distichum var. nutans by Melaleuca quinquenervia in southern Florida. In Ewel, K.C. & Odum, H.T. (Eds) Cypress swamps, pp. 358‑364. Univ. Florida Press, Gainesville.
Pierre Binggeli
May 1997

Miconia calvescens DC. (Melastomataceae)
M. magnifica Triana
Small tree from the neotropics invading disturbed areas and natural forests in the Society and Hawaiian Islands. It regenerates freely under canopy to eventually form monotypic stands. Many endemic species are being displaced and are thought to be at risk.

Species characteristics
Life form, size and lifespan
Small tree, up to 15 m tall, bearing large leaves (up to 1 m long) which are often green with three pale green nerves above and purple-blue below.
Taxonomy, variation and plasticity
Trees with bicoloured leaves are restricted to Central America while the other form occurs in both Central and South America.
Breeding system and reproductive biology
Small white and slightly fragrant flowers are borne in large panicles. Both allo- and autogamy occur, particularly in isolated individuals. Infructescences bear up to 500 blue-black fleshy berries (ca 0.6-0.7 cm in diameter) each containing around 140-230 seeds (size 0.7x0.5 mm). Flowering and fruiting may start within four years of germination. In Tahiti there are at least three peaks of flowering and fruiting per year. During the first fruiting season a young tree produces around 200,000 seeds on two infructescences and when older over 5 million seeds per year. Seed dispersal agents include gravity, wind, water, birds (mainly introduced species in the Society Islands) and small mammals, the latter two being the main agents. In Tahiti M. calvescens produces a large seed bank (up to 50,000 seeds m-2) where seeds are viable for more than two years and seeds germinate from fruits left in water for three months. Germination (rate up to 90%) is staggered and may take place under all light regimes including low light intensities (down to 0.02% of full sun light). Microsite requirements are varied and germination may even take place on rocks and the bark of trees.
Vegetative propagation
Vegetative layering and resprouting occur.
Light requirements and successional status
Miconia is shade-tolerant but it regenerates freely and grows more rapidly in forest gaps and open areas. In its native range is commonly found in disturbed areas.
Pests and diseases
No information is available.
Mycorrhizal associations and nitrogen fixation
Not reported.
Products and uses
Introduced to European botanical gardens and commonly cultivated in greenhouses because it had "one of the best and most striking of all conservatory foliage objects". Currently sold as an ornamental plant in the tropics.
Status in native range
Range and abundance
Natural distribution extends from southern Mexico (18o N) to southern Brazil (26o S). It is absent from most of the Amazon basin and the north coast of South America.
Climatic requirements
Its distribution suggests a wide climatic amplitude with a preference for tropical climates with distinct seasonality.
Site requirements 
Generally found in old pastures, forest edges, river banks, trailsides, roadsides and disturbed areas and sometimes in natural forest from sea level to 1800 m.
Weediness
This species is never common even in disturbed areas.
Status in invaded regions
History of introductions and intensity of invasions
Introduced to Tahiti in a private botanic garden in 1937 and some years later planted at the Agriculture Research Station (Taravao). Introductions to the nearby islands of Moorea and Raiatea are thought to be the result of, respectively, wind-dispersal or hikers and contaminated soils (coffee and timber saplings).
Patterns of invasion and time-lag
In Tahiti, the spread of M. calvescens was not noticed until 44 years after its introduction, however by that stage the species was already widespread. In Hawaii M. calvescens began to spread as soon as the introduced trees started fruiting and this would suggest that in the Society Islands the observed time-lag is not an ecological phenomena but, rather, a human perception problem. In Hawaii the plant was detected twenty years after its introduction and only following warnings emanating from French Polynesia as to the threat posed by the species.
In the Society Islands M. calvescens has spread into disturbed areas (i.e. roadsides, abandoned pasture and forest edges) and into natural forests. In forests it regenerates under canopy, and became the dominant canopy tree over large areas of Tahiti particularly after hurricane-induced disturbance. The ability of M. calvescens to dominate oceanic island tropical rain forests is linked to the low stature of the trees found in these forests.
Range and abundance
It dominates forests over 70% (ca 70,000 ha) of the island of Tahiti.
Site and climate
The climate of the Society Islands is tropical oceanic with two seasons, one warm and humid and the other, between March and November, is cooler and drier. Mean annual temperature is 26°C and rainfall varies greatly with an average of 1700 mm/yr. M. calvescens is found between 10 and 1300 m a.s.l. and in areas with more than 2000 mm of rainfall per year.
Floristic region and vegetation types
The Society Islands have 623 native species, of which 273 are endemics, and over 1500 species have been introduced. The original vegetation was dominated by forests.
Pests and diseases
Specific natural enemies have not been found.
Impact on ecosystem
M. calvescens has dramatically altered natural forests of the Society Islands. Native species are unable to tolerate the heavy shade cast by M. calvescens and are displaced. As a result, half of all endemic species are though to be at risk. The superficial and tentacular rooting system is thought to contribute to landslides.
Impact on humans and related activities
No obvious negative effects besides altering the physiognomy of the forested landscape.
Control
In the Society Islands and Hawaii major educational and control programmes have been initiated. Besides preventing the introduction of M. calvescens to other islands, eradication of the species from lightly infested islands has been attempted. Small individuals are uprooted while large one are cut and treated with herbicide (2,4-D) to prevent resprouting.
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
No native species appear to have life history characteristics (rapid growth (up to 1 m/yr), small seeds, profuse seed production, seed bank, shade tolerance etc.) similar to those of M. calvescens.
Differences in status and ecology between invaded and native ranges 
In the neotropics M. calvescens is not abundant and never dominates vegetation as it does in Pacific islands and this may result from the absence of natural enemies in the introduced range. The altitudinal range of the species is wide in both the native and introduced ranges.
Selected references 
** Conant, P., Medeiros, A.C. & Loope, L.L. (1997) A multiagency containment program for Miconia (Miconia calvescens), an invasive tree in Hawaiian rain forests. In Luken, J.O. &
Thieret, J.W. (Eds) Assessment and management of plant invasions, pp. 249‑254. Springer, New York.
**• Meyer, J.‑Y. (1996) Status of Miconia calvescens (Melastomataceae), a dominant invasive tree in the Society Islands (French Polynesia). Pac. Sci. 50, 66‑76. 
** Meyer, J.‑Y. & Florence, J. (1996) Tahiti's native flora endangered by the invasion of Miconia calvescens DC. (Melastomataceae). J. Biogeogr. 23, 775‑781.
** Meyer, J.‑Y. & Malet, J.P. (1997) Study and management of the alien invasive tree Miconia calvescens DC. (Melastomataceae) in the islands of Raiatea and Tahaa (Society Islands, French
Polynesia): 1992‑1996. Coop. Nat. Park Res. Studies Unit, Techn. Report 111, 1‑56.
** Meyer, J.‑Y. & Smith, C.W. (Eds) (1998) Proceedings of the First Regional Conference on Miconia Control. Gouv. de Pol. franç./Univ. of Hawaii at Manoa/Centre ORSTOM de Tahiti.
•# Wurdack, J.J. (1980) Miconia calvescens DC. In Harling, G. & Sparre, B. (Eds) Flora of Equator, 13, 171‑172. University of Göteborg and Riksmuseum, Stockholm.
Pierre Binggeli
May 1998

Mimosa pigra L. (Mimosaceae)
Thorny shrub from tropical America rapidly spreading in northern Australia and Thailand. In Australian floodplains it forms self-regenerating monotypic stands.

Species characteristics
Life form, size, lifespan
Spreading thorny shrub usually up to 2 m tall but occasionally to 6 m. Maximum age is about 5 years.
Taxonomy, variation and plasticity
There are two varieties, var. pigra and var. berlandieri which differ slightly in pod pubescence and spine morphology. Only the former has spread around the world.
Reproductive biology
Flowering may start within a year of germination. The bee-pollinated inflorescences, containing up to 100 flowers, are spherical, pink and last one day. On main branches one inflorescence is produced daily for five months during the rainy season. In Australia it has been suggested that most of the seeds are produced by autogamy, although wind pollination can not be ruled out. The hairy pods are up to 15 cm long and contain 8 to 24 seeds (each seed is ca. 5 x 2.4 mm and weighs 0.09 mg). The fruits ripen in ca. 3 months and when mature fragment into indehiscent one-seed segments. The bristles covering the pods facilitate floating and enhance dispersal along river systems. In evergreen forests a few flowers and fruits are found throughout the year. In Australasia in permanently moist sites flowering occurs all year round and on average < 5% of flower buds produce seeds. Anthesis takes place about 8 days after bud formation and another month is necessary for the production of mature seed pods. In northern Australia the soil seed banks can reach up to 12 000 seeds m-1 and seeds remain viable for more than two years. Seeds generally germinate when they are first wetted and the germination rate is high.
Resilience and resistance
In seasonally flooded areas fibrous adventitious roots develop around the base of the multiple stems. Mycorrhizae have been found associated with few strains of Rhizobium. However these associations are rare and it is not clear how important a source of nitrogen they are to populations of M. pigra. Following natural fires the plants resprout freely. The shrub does not naturally reproduce vegetatively.
Environmental requirements and successional status
Although adapted to seasonally flooded habitats M. pigra can regenerate under some degree of canopy cover.
Products and uses
It has been used as green manure and cover crop and is used as firewood and bean poles in Thailand. Utilized against snake bites.
Status in native range
Range and abundance
Native to Mexico, Central and South America
Climate
Dry to seasonally wet.
Site requirements 
In Costa Rica the M. pigra natural habitats are the banks of large rivers and marsh edges. Currently occupying similar habitats such as road sides and marshy spots in open pastures.
Weediness
In Costa Rica M. pigra is probably much more common now than prior to European colonisation. Its seeds appear to be spread by road construction equipment and thus the plant is typical of roadsides.
Pests and diseases
Leaflets fed upon by a number of beetle species but avoided by cattle and horses. In Costa Rica, seeds are heavily predated by beetles.
Status in invaded regions
History of introductions and intensity of invasions
M. pigra is widely distributed in Africa but unclear how it got there from Tropical America. Introduced, as an ornamental or seed contaminant, to the Darwin Botanic Gardens of Australia's Northern Territory prior to 1891. The spreading population is thought to be the result of a single introduction. During the second part of this century M. pigra has spread dramatically to form monotypic stands in floodplains. Introduced to Thailand in 1947 as green manure and cover crop and being prickly it was thought it would restrict access to water banks as thus reduce erosion. Now it covers large areas of standing waters and water banks. Also spreading in Indonesia and peninsular Malaysia. Long-distance dispersal is possible when cattle are transported and in Thailand road transportation spread seeds along highways.
Patterns of invasion and time-lag
Although introduced to Australia last century M. pigra remained an occasional nuisance around Darwin. It started to spread in the late 1950 when it reached the open floodplains and started to spread to increase dramatically in the 1970s. The time-lag resulted from the inability of the species to reach suitable habitats. The rate of population increase is high (r of ca. 0.66 per year). Once established as monotypic stands, M. pigra can regenerate under its own canopy. In these stands the half life of plants taller than 20 cm varies between 13 and 22 months depending on soil types. M. pigra can also regenerate under canopy of Melaleuca fringing the floodplains. 
Site and climate
M. pigra is found in tropical regions with > 750 mm annual rainfall unless growing around dams and watercourses. It does not appear to have any soil type preferences, but is more commonly found in moist situations such as floodplains and river banks. 
Floristic region and vegetation types
It invades sedgeland and grassland communities on open floodplains and Melaleuca forest fringing the floodplains. It is not found in tropical rain forest areas (rainfall > 2250 mm). 
Pests and diseases
Ungulates have little impact on M. pigra and some post dispersal seed predation occurs.
Impact on ecosystem
M. pigra completely alters floodplain and swamp forest of northern Australia. Its main impacts are: fewer birds and lizards, less herbaceous vegetation and hinders tree regeneration. If the spread of M. pigra is not halted it may affect the touristic value of the Kakadu National Park as many visitors come to see the wetlands birdlife. In Thailand it interferes with irrigation systems (sediment accumulation) and access to electric power lines and is a safety hazard along roads. It also grows in fallow rice paddies making reclamation more expensive. It is a source of firewood and bean poles and its foliage can be used as an animal feed.
Impact on humans and related activities
In Australia M. pigra poses a threat to the cattle industry as it invades buffalo pasture. It also restricts access to waterways for humans, particularly fishermen.
Control
In Australia Neotropical biological control agents are being actively investigated as classical introductions while chemical control is used to contain the spread and eradicate new infestations. Aerial spraying of gelled gasoline followed by fire kills stands of M. pigra and soil surface seeds, however it enhances buried seed germination. Effective control is difficult because of the large soil seed bank.
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
In the floodplains of northern Australia there are no woody plants present. 
Differences in status and ecology between invaded and native ranges 
The main difference appears to be habitat availability. In northern Australia large treeless floodplains exist which doe not appear to be the case in tropical America. A comparison of phytophagous insect fauna between Australia and Mexico showed that in the invaded region there were fewer insect species, more species were polyphagous and fewer feed externally. In Mexico many insects feed on new growth and inside the reproductive structures but such damage was not observed in Australia.
Selected references 
• Janzen, D.H. (1983) Mimosa pigra (Zarza, Dormilona). In Janzen, D.H. (Ed.) Costa Rican natural history, pp. 277‑278. The University of Chicago Press, Chicago.
** Lonsdale, W.M. (1993) Rates of spread of an invading species ‑ Mimosa pigra in northern Australia. J. Ecol. 81, 513‑521. 
* Lonsdale, W.M. (1994) Inviting trouble: introduced pasture species in northern Australia. Aust. J. Ecol. 19, 345‑354. 
*# Lonsdale, W.M., Miller, I.L. & Forno, I.W. (1989) The biology of Australian weeds. 20. Mimosa pigra L. Pl. Prot. Quart. 4, 119‑131.
** Robert, G.L. & Habeck, D.H. (Eds) Proc. int. symp. Mimosa pigra management, Chiang Mai. I.P.P.C., Corvallis. 
* Wilson, C.G., Flanagan, G.J. & Gillett, J.D. (1990) The phytophagous insect fauna of the introduced shrub Mimosa pigra in northern Australia and its relevance to biological control. Environ. Entomol. 19, 776‑784.
Pierre Binggeli
May 1997

Myrica faya L. (Myricaceae)
Macaronesian endemic introduced to Hawai'i in the 19th century. Following extensive reclamation planting, it has spread into a variety of habitats including natural forest, lava flows, roadsides and abandoned pasture.

Species characteristics
Life form, size, lifespan
Evergreen tree to 12 m tall. Often multi-stemmed.
Taxonomy, variation and plasticity
No information is available. However the species is found on isolated islands and under varying climatic conditions and this would suggests that some variation must exist between provenances.
Reproductive biology
M. faya is considered to be a dioecious species, however 'male' plants often produce some fruits and 'female' individuals a few male inflorescences. It appears to be a wind-pollinated species although in Hawai'i it is visited by the introduced Apis mellifera. The edible black drupe (6mm in diameter containing 1-5 seeds) is bird-dispersed in its native range but in Hawai'i it is dispersed by birds (mainly introduced) and feral pigs. About 20,000 seeds per tree are produced every year. In Hawai'i fruits ripen primarily between August and November but may be produced all year round. Seed germination decreases from 80% at 10 weeks to 30% after 78 weeks of dry storage. Passage through birds has no effect whereas its own leaf litter reduced germination. Germination occurs at all light levels but is highest under 55% and 63% of shade. 
Resilience and resistance
Nitrogen fixing species which can colonize lava flows. In the Azores it is wind resistant although the bushes are only 2‑3 m tall and are much flattened and bent. Allelopathic effect has been suggested. Burnt trees may resprout.
Environmental requirements and successional status
Although adapted to colonize old lava flows, M. faya is a main component of old forests. Regenerates freely under open canopy but not under full canopy.
Products and uses
In Hawaii Portuguese labourers made wine from the fruit.
Status in native range
Range and abundance
Restricted distribution to the Macaronesian islands of the Azores, Madeira and the Canary Islands. The tree is common in most remaining evergreen forests. 
Climate
In Canaries the climate is typically mediterranean with wet winters and dry summers. The climate of the Azores is affected by the Gulf Stream with no frost below 500 m and average summer and winter temperatures of respectively 21C and 14.5C. Madeira's climate is intermediate. Rainfall on all islands increases with altitude (varying between ca. 750 mm and 2500 mm) and highlands are often covered with cloud and mist.
Site requirements 
In the lowland Azores, much altered by man, Myrica faya is the main species to have regenerated on old lava flows. Around an altitude of 600 m, where some natural forest remains, M. faya is codominant in the canopy (5-6 m tall) and sometimes is an emergent. Distribution up to 900 m a.s.l. The species does not appear to regenerate under canopy. 
Weediness
No sign of weediness. In fact in the Azores the forests, where M. faya is codominant, are invaded by Pittosporum undulatum, native of eastern Australia.
Pests and diseases
Suffers from a number of diseases resulting in canker, dieback and root rot.
Status in invaded regions
History of introductions and intensity of invasions
Introduced into Hawaii by immigrants from the Azores and Madeira in the late 1800s, probably as an ornamental or medicinal plant. Extensively planted for watershed reclamation in the 1920s and 1930s. Now present on several Hawaiian islands and by 1985 covered 12,200 ha of the Hawaii Volcanoes National Park (HVNP) and considered one of the main noxious species. Common on pasture land.
Patterns of invasion and time-lag
On young, volcanically disturbed soils M. faya rapidly forms dense monotypic stands but does not readily invade closed, late-successional native forest. In HVNP birds disperse the seeds to perch trees, the native Metrosideros polymorpha. Under tree canopy seed densities of 6 to 60 seeds.m-2.yr-1 are found whereas they are absent in the open. Seeds germinate and seedling become established under M. polymorpha canopies.
Natural spread was reported within years of the watershed planting which was then halted. It was first reported in undisturbed areas of the HVNP in 1961 and by 1973 the population was large enough to warrant control.
Site and climate
M. faya  is found between 150 to 1310 m a.s.l. in mesic to wet forest. At the altitude of 1250 m, where most of the HVNP invasion is taking place, the mean annual rainfall is ca. 2400 mm without a distinct dry season and the mean January and July temperatures are, respectively, 14°C and 17°C. Very occasional frosts occur. 
Floristic region and vegetation types
The Hawaiian islands are rich in endemic species and are very susceptible to plant invasions particularly in lowland regions. Other woody plants are invading are invading plant communities invaded by M. faya.
Pests and diseases
Some seeds are eaten by rats.
Impact on ecosystem
M. faya changes ecosystem function by altering the nitrogen cycle. Its litter inhibits germination and seedling establishment of the native tree Metrosideros polymorpha. Monospecific stands have virtually no understorey.
Impact on humans and related activities
Not reported.
Control
In the HVNP control was initiated 22 years after M. faya was first recorded. Over four years 92,000 individuals were removed, yet 609 ha of moderate density populations remained and the control programme was abandoned. The use of chemical control in native vegetation, some of which is threatened or endangered, is avoided. Biological control of M. faya is being investigated.
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
Apparently the actinorrhizal symbiosis, characteristic of M. faya and other species colonizers of low-nitrogen sites, was absent from the native flora of Hawai'i. In competition with the native tree Metrosideros polymorpha, M. faya diameter and height growth is always greater in all size classes.
Differences in status and ecology between invaded and native ranges 
M. faya is invasive in Hawaii and is considered a weed whereas in the Azores, where it is native and codominant in evergreen forest, it often fails to regenerate and its habitat is invaded by Pittosporum undulatum. Both the native and invaded ranges are rich in endemic species but have relatively few tree species. The time-lag between the lava flow formation and M. faya colonisation appear to be much shorter on Hawai'i than on  the Azores.
Selected references 
•  Gardner, D.E. & Hodges, C.S. (1990) Diseases of Myrica faya (firetree, Myricaceae) in the Azores, Madeira and the Canary Islands. Plant Pathol. 39, 326‑330.
• Haggar, J.P. (1988) The structure, composition and status of the cloud forests of Pico Island in the Azores. Biol. Conserv. 46, 7‑22. 
# Little, E.L. & Skolmen R.G. (1989) Common forest trees of Hawaii (native and introduced). Agric. Handbook 679. US Forest Service, Washington.
** Vitousek, P.M. & Walker, L.R. (1989) Biological invasion by Myrica faya in Hawai'i: Plant demography, nitrogen fixation, ecosystems effects. Ecol. Monogr. 59, 247‑265. 
** Vitousek, P.M., Walker, L.R., Whiteaker, L.D., Mueller‑Dombois, D. & Matson, P.A. (1987) Biological invasion by Myrica faya alters ecosystem development in Hawaii. Science 238, 802‑804.
** Walker, L.R. & Vitousek, P.M. (1991) An invader alters germination and growth of a native dominant tree in Hawai'i. Ecology 72, 1449‑1455.
Pierre Binggeli
May 1997

Passiflora mollissima HBK. Bailey (Passifloraceae)
Andean woody climber cultivated in tropical and warm-temperate zones for its edible fruit and attractive flowers. It has become a serious pest in the forests of Hawai'i.

Species characteristics
Life form, size and lifespan
Perennial woody vine reaching a length of 20 m and an age of 20 years. Usually climbing but in absence of support is either shrubby or trailing.
Taxonomy, variation and plasticity
In its native range P. mollissima is morphologically variable and frequently hybridizes with other species. In Hawai'i, at the exception of flowering and fruiting, the plant's phenology is variable. In East Africa two distinct forms occur.
Reproductive biology
The nectariferous flowers are large (5-10cm in diameter), pinkish, and borne singly at base of tendrils. They visited by a large number of insects and birds but are chiefly pollinated by honeybees and syrphids. Although mainly outcrossed, selfing occurs. Flowering and fruiting starts when the plant is one year old. The large yellowish fleshy fruits (5 cm) containing 180 seeds (? 6 mm) ripen in ca. 3 months and in Hawai'i are produced throughout the year with a peak during the wet season (December-March). Fruits are widely dispersed locally by native and alien birds and mammals but long distance dispersal also occurs. In New Zealand 50% of seeds survived burial for 66 weeks at 9 cm, and subsequently germinated. Seed germination is staggered with a peak within eight weeks following the breaking of dormancy.
Resilience and resistance
Has a high capacity for vegetative propagation, with the interconnected portions decaying. The plant is frost tolerant.
Environmental requirements and successional status
P. mollissima tolerates both high and low light levels. A seedling bank is commonly found under tree canopy although newly germinated seedlings do not tolerate dense shade. Optimal growth occurs in full sun light.
Products and uses
Species is widely cultivated in its native range and in many parts of the tropics and sub-tropics as an ornamental and for its fruits.
Status in native range
Range and abundance
Native to the tropical region of the Andes between 2000 and 3600 m a.s.l. Original distribution is unclear as the species has been widely cultivated. Natural populations are scattered and sparse.
Climate
Seasonal climate typically with a 2 months dry period and a mean annual temperature and rainfall of respectively ca. 13°C and ca. 1300 mm. P. mollissima tolerates occasional frosts.
Site requirements 
Not known
Weediness
Not reported.
Pests and diseases
Fungal pathogens and insects attack the fruits. 
Status in invaded regions
History of introductions and intensity of invasions 
Introduced to many tropical countries. First introduced to the island of Hawai'i around 1920. Subsequently introduced to several other sites on Hawai'i and two other nearby islands. P. mollissima occupies large areas on three Hawai'ian islands and may form continuous cover. Described as weedy in some parts of New Zealand and appears to have naturalised in some South African forests. In East Africa it is cultivated as an ornamental and often escaped, growing in forest edges and clearings.
Patterns of invasion and time-lag
Establishment and growth of P. mollissima increase with increasing light intensity. The densest infestations are found in openings and forest margins. In the forest environment a seedling bank exist and the seedlings are released as soon as a gap is formed in the canopy. In smaller gaps P. mollissima may fail to reach canopy height prior to gap closure. Once the vines have reached canopy height, they spread laterally. Increased disturbance increases the rate of the invasion particularly as a result of feral pig activity, logging or hurricanes. It appears that no time-lag occurred in Hawai'i between the timing of the various introductions and that of the plant's spread. 
Site and climate
In Hawai'i, P. mollissima occurs between an elevation of 500 and 2500 m. It tolerates a wide variation in climate with a range of mean annual rainfall and temperatures of respectively 1250-2000 mm and 11-24C. Short dry season occurs in June-July.
In New Zealand the vine is found in areas with a mean annual temperature of 11.4 to 15.0°C and rainfall of 800 to 1200 mm.
Floristic region and vegetation types
The Hawai'ian islands are rich in endemic species but are prone to biological invasions by a wide array of plants and animals. P. mollissima is spreading into native forests, scrub vegetation, pastures, forestry plantations and lava flows.
Pests and diseases
Several fungal pathogens attack fruits but do not limit fruit production. In damper areas they suffer from slug herbivory.
Impact on ecosystem
In Hawai'i P. mollissima has a major impact on vegetation including suppression of tree regeneration, toppling of shallow-rooted trees, death of standing trees through shading and lowered species richness. Continuous prolific fruit production lead to an increase in population densities of exotic mammals, e.g. feral pigs.
Impact on humans and related activities
P. mollissima has no economic value in the tropics, while in New Zealand it is widely grown as a fruit and sold. It is a major problem in forestry, particularly following logging.
Control
Mechanical, chemical and biological means of control have been attempted with limited success in the tropics. In New Zealand cutting vines and wetting cuts with herbicide, particularly Tordon or Roundup, is effective although follow-up treatment may be required.
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
There does not appear to be any ecological equivalent in Hawai'i.
Differences in status and ecology between invaded and native ranges
In Hawai'i, as opposed to South America, the species does not vary morphologically. Fruit set is greater in Hawai'i than in South America and this probably result from the lower insect herbivory suffered by flowers and fruits in the invaded range. Densities of P. mollissima in Hawai'i are far greater than those observed in the Andes.
Selected references 
* LaRosa, A.M. (1984) The biology and ecology of Passiflora mollissima in Hawai'i. Univ. Hawaii Coop. Natl Park Resour. Stud. Tech. Rept 50, 1‑168. Botany Dept, University of Hawaii, Honolulu.
** LaRosa, A.M. (1992) The status of banana poka in Hawai'i. In Stone, C.P., Smith, C.W. & Tunison, J.T. (Eds) Alien plant invasions in native ecosystems of Hawai'i: management and research, pp. 271‑299. University of Hawaii Press, Honolulu. 
* Markin, G.P., Lai, P.‑Y. & Funasaki, G.Y. (1992) Status of biological control of weeds in Hawai'i and implications for managing native ecosystems. In Stone, C.P., Smith, C.W. & Tunison, J.T. (Eds) Alien plant invasions in native ecosystems of Hawai'i: management and research, pp. 466‑482. University of Hawaii Press, Honolulu.
* Russell‑Smith, J. & Bowman, D.M.J.S. (1992) Conservation of monsoon rainforest isolates in the Northern Territory, Australia. Biol. Conserv. 59, 51‑63.
#* Wilde, W.J.J.O. de (1975) Passifloraceae. In Polhill, R.M. (Eds) Flora of tropical East Africa. Crown Agents for Oversea Governments and Administrations, London.
** Williams, P.A. & Buxton, R.P. (1995) Aspects of the ecology of two species of Passiflora (P. mollissima (Kunth) L. Bailey and P. pinnatistipula Cav.) as weeds in South Island, New Zealand. N.Z. J. Bot. 33, 315-323.
Pierre Binggeli 
May 1997

Pinus patula Schiede & Deppe (Pinaceae)
Widely planted timber tree from the Mexican uplands. It is invading montane areas of Malawi and Hawaii. Its spread is facilitated by fire in grasslands and logging in natural forests. The tree's spread threatens some endemic.
.
Species characteristics
Life form, size and lifespan
Evergreen tree 20 to 30 m tall.
Taxonomy, variation and plasticity
Sometimes difficult to distinguish from forms of related species. Some morphological characters show marked clinal variation in Mexico.
Reproductive biology
Flowering may start when the tree is two years old. Female flowers usually appear a year later than male flowers and are respectively borne in the upper and lower parts of the canopy. In Hawaii and Malawi P. patula starts producing many cones after 6 to 8 years. In Africa seed set varies from 45 to 93 seeds per cone out of a potential 200 to 300, whereas a Mexican collection had only 22 seeds per cone. Cones take 22 months to reach maturity and may remain closed several years until they are scorched by fire. Then the wind-dispersed seeds (4 mm long with a 1 cm long wing, weight = < 0.1 mg) are released and have a high germination capacity (ca 85%). In tropical Africa it appears to set seed freely every year in upland areas between 1000 to 1700 m.
Resilience and resistance
Although easily killed by fire, P. patula is adapted to it as its serotinous cones release seeds after burning and seedling establishment is favoured by bare mineral soil. It possesses mycorrhizal associations and plantations in Malawi failed until they were brought into the country.
Environmental requirements and successional status
The tree requires deep acidic soils with a good moisture supply. In Mexico it often forms monotypic stands or is found in mixtures with other pine species.
Products and uses
Important timber, pulpwood and fuelwood in many parts of the world.
Status in native range
Range and abundance
Native to the highlands of Mexico where it has a restricted distribution (18N to 24N). It forms pure dense stands.
Climate
Warm temperate region where the rainfall varies between 1000 and 2000 mm mainly falling during the summer months. Occasional frosts occur.
Site requirements 
The species occurs mainly on the eastern side of mountains at an altitude between 1650 and 3000 m. It is found in areas with deep well drained sandy loam.
Weediness
Not reported.
Pests and diseases
Seed set often prevented by rust fungus.
Status in invaded regions
History of introductions and intensity of invasions 
It is grown in many parts of the world in large plantations. First introduced to Malawi in 1923 and to Mount Mulanje (16°S, 35°E) in 1946 when forestry trial plots were established. In the 1950s large-scale forestry plantings were undertaken. Originally P. patula was planted as a nurse crop for the native timber tree Widdringtonia cupressoides (L.) Endl. but the objective was never achieved. In Hawai'i it invades native shrubland in the Haleakala National Park.
Patterns of invasion and time-lag
P. patula is spreading in both grassland and native forest. Regeneration is greatest in the vicinity of plantations but isolated trees became established several km away from the plantations and within 10 years became foci for further spread. In natural forest the pine density tends to increase with logging intensity. The current fire regime is the main factor facilitating the spread of this fire-adapted tree in grasslands. However, it appears that the increased dead matter increases the intensity of fires which has resulted in the death of some pine stands. The impact of variation in fire cycles and intensity on the invasion have yet to be investigated. 
Site and climate
The Mulanje Mountain consist of a series of plateau around 1800 m with peaks reaching 3000 m. Mt Mulanje rises abruptly from the surrounding plain (600-700 m) and is isolated from other central African mountains. P. patula is found in a number of plant communities between 1800 and 2400 m. On most of the mountain rainfall is seasonal (mainly summer) and is around 2000-3000 mm per annum on the plateau where night frosts regularly occur. Soils (ferallitic latosols) are acidic (pH ca 4.2)
Floristic region and vegetation types
These mountains are covered by a variety of vegetation types varying with altitude, including forests and grasslands, containing a number of endemic species and invaded by several introduced species. The plateau vegetation is grassland, maintained by fire, and interspersed with forest in sheltered hollows and ravines. Lower elevation vegetation types, but particularly forests, are much destroyed and threatened by human activities.
Pests and diseases
The species is generally considered free of pests and diseases by foresters although lepidoptera do pose a threat in some regions.
Impact on ecosystem
There are indications that P. patula alters the species composition of invaded forest and grasslands and it appears to exclude some uncommon endemic ground flora species. It displaces W. cupressoides, Malawi's national tree, which although not endemic to Mulanje, only reaches its full height (ca 40 m) there. An important component of the shrub layer under P. patula is the invasive Rubus ellipticus.
Impact on humans and related activities
P. patula timber is worth twenty times less than that of W. cupressoides.
Control
Trees are cut near the ground and the slash is stacked in piles. Follow-up operations, preferably burning, are essential within a year or two to eliminate seedlings. The eradication of P. patula from Mt Mulanje has been recommended. Apart from control measures carried out by I. Sakai, a Japanese volunteer, and controlled yearly fires are lighted around the perimeter of the pine plantations killing young seedlings, the recommendations have not been implemented. 
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
There are no native pine species in Malawi. In the absence of P. patula and the native W. cupressoides would spread into the secondary scrub and occasionally into short grassland. Although highly susceptible to fire, W. cupressoides can become dominant if sufficiently fierce periodic fires occur to kill broadleaved trees. However, W. cupressoides is much slower growing than P. patula and in the presence of the latter succession will result in a P. patula dominated canopy. W. cupressoides competitive ability has been further diminished as it has recently suffered from the introduction of the cypress aphid, Cinara cupressi, resulting in the poor health or death of many trees.
Differences in status and ecology between invaded and native ranges
No apparent differences in site requirements or ecology between native and invaded regions exist. In its native range P. patula often compete with other pine species and seed set is affected by fungus.
Selected references 
* Bone, R. (1995) The effects of Pinus patula invasion in the indigenous and grasslands of Mount Mulanje, southern Malawi. B.Sc. Thesis, University of Aberdeen. 
* Chapman, J.D. (1994) Notes on Mulanje cedar - Malawi's national tree. Commonw. For. Rev. 74, 235-242.
* Chapman, J.D. (1994) Mt. Mulanje, Malawi. In Davis, S.D., Heywood, V.H. & Hamilton, A.C. (Eds) Centres of plant diversity, a guide and strategy for their conservation. Vol. 1. Europe, Africa, south-west Asia and the Middle East, pp. 240-247. IUCN & WWF, Gland.
* Edwards, I. (1982) Plant invaders on Mulanje Mountain. Nyala 8, 89‑94.
* Sakai, I. (1989) The problem of Pinus patula on Mulanje Mountain, its threat, and proposed measures for eradication. Forest Res. Inst. Malawi Rep. No. 89006. 
* Verboom, G.A. (1992) A report on the invasive status of Pinus patula on Mount Mulanje, Malawi. B.Sc. Thesis, University of Cape Town.
•#* Wormald, T.J. (1975) Pinus patula. Tropical Forestry Papers No. 7. Dept of Forestry, Oxford.
Pierre Binggeli 
May 1997

Pittosporum undulatum Vent. (Pittosporaceae)
Large ornamental temperate/sub-tropical forest tree, native of south-east Australia. Introduced to various temperate and tropical regions including Jamaica, where it invades natural forest.

Species characteristics
Life form, size, lifespan
Large evergreen tree growing to 30 m, lifespan unknown.
Taxonomy, variation and plasticity
P. undulatum is well defined taxonomically, though it hybridises with P. bicolor and perhaps P. revolutum in Australia. 
Reproductive biology
Sex expression of flowers is somewhat variable but flowers are usually unisexual. Inflorescences (cymose) bear between 1 and 4 insect‑pollinated flowers. Flowering starts at around 5 years of age and is enhanced by higher light levels. Fruits (capsules, ca. 12 mm across) take about 6 months to mature. Fruiting is highly synchronised in Jamaica. The capsules usually contain 20‑40 sticky orange seeds, which are bird‑dispersed. 
Resilience and resistance
Seedlings coppice if the shoot is removed and blown‑down trees sprout vigorously along the trunk. Cut stems resprout if replanted. The species is moderately susceptible to fire. VA mycorrhizae have been observed on P. undulatum in Jamaica.
Environmental requirements and successional status
Seedling recruitment occurs below the forest canopy but increases in higher light intensities (i.e. in gaps) with seedling densities up to 5000 m‑2. Few seeds germinate under P. undulatum canopies. It can become dominant in Australia and elsewhere.
Products and uses
P. undulatum makes very good firewood, produces excellent charcoal and is a useful all purpose timber. It is an ornamental tree with attractive fragrant flowers. Abundant nectar production makes it good for honey bees.
Status in native range
Range and abundance
P. undulatum is native to the coastal belt and mountains of south‑eastern Australia from Biggenden in Queensland to the south of Victoria. It is a common sub‑canopy tree and shrub in several forest types and is also widespread in more open habitats.
Climate
The climatic conditions of its native range vary from moist sub‑tropical to dry temperate (without a pronounced dry season).
Site requirements 
P. undulatum is found in a variety of habitats, such as rain forest, scrub, gullies and grassland (if fire is suppressed). In the drier parts of the range it is restricted to moister sites. Fire limits its range and as the fire regime in the 20th century has decreased as a result of human management, P. undulatum has been able to spread to areas where previously it would have been killed.
Weediness
It is spreading outside its pre‑European settlement range in several parts of Australia, a result of widespread planting in gardens, the fire suppression policies in many areas close to habitation and the introduction of the European blackbird, Turdus merula.
Pests and diseases
About 10 insect species in Australia feed on P. undulatum but none are believed to cause serious damage or death or significantly reduce population levels.
Status in invaded regions
History of introductions and intensity of invasions
Introduced to Jamaica in 1883 and planted in the Cinchona Botanic Gardens situated at 1450 m in the Blue Mountains. Found throughout a large part of the western end of the Blue Mountains and dominant in many areas of secondary forest close to Cinchona, locally common in more primary forest.
P. undulatum invades the Eucalyptus forests of central Victoria (Australia) where it is considered a threat to the survival of the native forests. It is invading a number of Pacific and Atlantic ocean islands. P. undulatum is spreading into scrub and riverine forest in Cape Province, South African fynbos but it has recently been affected by severe die‑back.
Patterns of invasion and time-lag
P. undulatum seedlings emerge after periods of wet weather, but not beneath dense canopy cover. However the rate of spread of P. undulatum increases with large‑scale disturbance such as that caused by hurricanes. Isolated P. undulatum trees occur several hundred metres from other trees of the same species.
There is no evidence for any appreciable time lag in the invasion, though the rate of invasion certainly appears to have accelerated since Hurricane Gilbert in 1988.
Site and climate
The Blue Mountains are very steep and rise to 2265 m. Mean annual rainfall is 2700 mm or more with two rainy seasons, though considerable variability in rainfall. Mean monthly maximum temperatures range from 18.5 to 20.5°C. Night‑time temperatures in winter can fall below 10°C. Hurricanes are quite frequent.
Floristic region and vegetation types
The Blue Mountains are covered with montane rain forests containing about 550 flowering plant species, of which about 85 are thought to be endemic to the range. Canopy height ranges from 5 m or less at high altitude to 25 m plus lower down.
Pests and diseases
In South Africa die-back has occurred as a result of a recent spread of an unidentified disease.
Impact on ecosystem
P. undulatum becomes dominant in secondary forests and natural forest subjected to hurricane damage. In areas invaded by P. undulatum a sharp decrease in native species richness has been recorded, probably because of the dense shade it casts.
Impact on humans and related activities
P. undulatum wood is preferred by locals for firewood and may have potential as a source of timber.
Control
Control has not been attempted but would be desirable. However due to the steep slopes and inaccessibility of the Blue Mountains traditional methods of control would be difficult. Furthermore, gap formation following cutting promotes the regeneration of P. undulatum and other alien weeds, notably Polygonum chinense and Hedychium gardnerianum. Biological control is being considered.
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
P. undulatum, when compared with native species, differs in its response to hurricane by lower mortality, less crown damage and higher rate of treefalls (trunks readily sprout after being blown down). Its crown is noticeably denser and extends further downwards than that of native species. The extensive superficial rooting system of P. undulatum is not observed in native species.
Differences in status and ecology between invaded and native ranges
The range in climates between its invaded and native ranges is considerable
Selected references 
•  Gleadow, R.M. (1982) Invasion by Pittosporum undulatum of the forests of central Victoria. 2. Dispersal, germination and establishment. Aust. J. Bot. 30, 185‑198. 
•  Gleadow, R.M. & Ashton, D.H. (1981) Invasion by Pittosporum undulatum of the forests of central Victoria. 1. Invasion patterns and plant morphology. Aust. J. Bot. 29, 705‑720.
** Goodland, T. & Healey, J.R. (1996) The invasion of Jamaican rainforests by the Australian tree Pittosporum undulatum. University of Wales, Bangor.
** Goodland, T. & Healey, J.R. (1997) The effect of Pittosporum undulatum on the native vegetation of the Blue Mountains of Jamaica. University of Wales, Bangor.
** Goodland, T. & Healey, J.R. (1996) The control of the Australian tree Pittosporum undulatum in the Blue Mountains of Jamaica. University of Wales, Bangor.
* Pickard, J. (1984) Exotic plants on Lord Howe Island: distribution in space and time, 1853‑1981. J. Biogeogr. 11, 181‑208.
* Richardson, D.M. & Brink, M.P. (1985) Notes on Pittosporum undulatum in the south western Cape. Veld and Flora 71, 75‑77.
** Rose, S. (1997) Integrating management of Pittosporum undulatum with other environmental weeds in Sydney's urban bushland. Pac. Conserv. Biol. 3, 350‑365.
Pierre Binggeli & Tom Goodland
May 1997

Psidium guajava L. (Myrtaceae)
Small evergreen weedy tree from tropical America introduced throughout the tropics for its edible fruits. It is spreading in pasture and agricultural land. On the Galapagos it is displacing evergreen forest composed of many endemic taxa.

Species characteristics
Life form, size, lifespan
Evergreen shrub or small wide-spreading tree 3-10 m high.
Taxonomy, variation and plasticity
Numerous varieties including yellow and red fruited ones. All cultivars are vegetatively propagated.
Reproductive biology
The white flowers are ca. 1.5 cm in diameter and are found singly or in cymes of 2 or 3 flowers. Flowers are pollinated by bees and other insects and cross-pollination accounts for about 35% of the seed set. The large pear-shaped fruit (5 cm long) is an edible berry and contains numerous seeds (size 3-5 mm). It is mainly distributed by cattle. The seed passage through the animals digestive tract does not appear to affect seed germination but seed losses occur as a result of food mastication. Seeds remain viable for several months and will germinate in 3-5 weeks in the warm season. Seed germination rates vary much from year to year and seedling establishment in cow pats is reduced by as much as 50% as shoots of germinated seeds deeply buried in the dung fail to reach the surface.
Resilience and resistance
P. guajava often suckers from roots near the base of the trunk, particularly after a light frost, to which the tree is susceptible. It tolerates temporary waterlogging. Following cutting it coppices readily and the tree spreads by suckering. It can also be propagated by layering or cuttings. P. guajava possesses vesicular-arboricular mycorrhizal associations.
Environmental requirements and successional status
It has an excellent ability to compete with weeds and grass. It can take over sites when it receives full sunlight but can withstand partial shading.
Products and uses
The wood makes excellent firewood and charcoal, and tool handles and implements can be made out of it. The fruits have a very high vitamin C content and red guavas are rich in vitamin A. They are made into preserves, jam, jelly and juice. The tannin-rich leaves and green fruits are used for dyeing and tanning.
Status in native range
Range and abundance
Native to the American tropics where it is widely cultivated.
Climate
It grows well in tropical areas of more than 1000 mm of rainfall and can endure droughts of 4 to 5 months.
Site requirements 
Found from sea level to 800 m and sometimes up to 1500 m, although its natural limit is unclear due to widespread planting. It favours slightly to strongly acid soils.
Weediness
It is a common pasture weed in central America either as scattered trees or in pure stands (264 trees/ha).
Pests and diseases
Many insects are reported to cause damage to the plant but particularly to its fruits.
Status in invaded regions
History of introductions and intensity of invasions
At an early date the Spanish brought P. guajava to the Philippines and the Portuguese to India, and it was then spread throughout the tropics. A tree from the Melbourne Botanic Gardens was introduced to Fiji in 1863, where the species has since become a major weed of pastoral, arable and plantation land. First introduced to the Galapagos around 1870 and is now found on three of the populated islands. It has invaded natural forest and covers large areas of these islands.
Patterns of invasion and time-lag
In agricultural areas it becomes a serious pest particularly as a result of root suckering induced by firewood cutting. It competes successfully with crop plants and grasses and soon forms thickets which smother grasses and reduce crop yields. In the Galapagos in 1922 it was already mentioned as a bad plague forming impenetrable thickets. It has replaced most evergreen forest on one of the islands and covers vast areas of the humid zones of four islands. The spread is facilitated by introduced cattle which eat the fruit and excrete the seeds. The dung provides a nutrient rich substrate and appear to reduce grass competition. Cattle also trample vegetation and create open spaces necessary for successful P. guajava seed germination and seedling establishment. Increased fire frequency increase P. guajava dominance.
Site and climate
In the tropics it becomes established under a wide variety of soil and climatic conditions, particularly rainfall.
Floristic region and vegetation types
Usually found on fallow land with highly modified flora. On the Galapagos the invaded vegetation contains a large number of endemic taxa and P. guajava is mostly found in the evergreen forest or scrub.
Pests and diseases
In Fiji P. guajava is attacked by the fungus Botryodiplodia theobromae which also attacks plantation crops. In India wilt is usually fatal where P. guajava occurs on soil with pH > 7.5. 
Impact on ecosystem
On the Galapagos Islands P. guajava outgrows native species and forms dominant stands suppressing the native flora. Its spread poses a threat to the survival of some of these endemic species.
Impact on humans and related activities
In Fiji the invasion of pasture land made livestock farming uneconomic in places and also provided an excellent breeding ground for insect pests. Despite the fruit's food value, it is considered a pest. In many regions it supplies valuable firewood and is a good food source.
Control
In the Galapagos restriction to cattle movement is the main factor which can slow the spread of the invasion both by preventing the dispersal of seeds and the production of regeneration sites. Established trees are cut and stumps painted with herbicide. In Fiji P. guajava has been most successfully controlled from arable land using mechanical means.
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
In the Galapagos most native tree species lack VA mycorrhizal associations and their existence in P. guajava may give it some competitive advantage. The introduced cattle facilitate the spread and regeneration of the invader but not that of endemic species. Some endemic and rare taxa have failed to regenerate following bush fires whereas P. guajava shows a high degree of survival and regeneration.
Differences in status and ecology between invaded and native ranges 
The spread in open areas is similar in both native and invaded ranges, however the ability to invade disturbed forest and dominate the native species is only observed on the Galapagos Islands.
Selected references 
# Anon (1983) Firewood crops; shrub and tree species for energy production, Vol. 2. National Academy of Science, Washington. 
# Anon (1986) Food and fruit‑bearing forest species. 3. Examples from Latin America. FAO, Rome. 
* Hamann, O. (1991) Indigenous and alien plants in the Galápagos Islands: problems of conservation and development. In Heywood, V.H. & Wyse Jackson, P.S. (Eds) Tropical botanic gardens: their role in conservation and development, pp. 169-192. Academic Press, London. 
** Partridge, I. (1979) The guava threat in Fiji. South Pacific Bull. 29(2), 28‑30.
** Nowak, J.B., Lawesson, J.E., Adsersen, H. & Vries, T. de (1990) A two‑year study of post‑fire vegetation dynamics on southern Isabela, Galapagos Islands, Ecuador. Monogr. Syst. Bot. Missouri Bot. Gard. 32, 123‑136.
# Purseglove, J.W. (1968) Tropical crops. Dicotyledons. Longman, London. 
* Schofield, E.K. (1989) Effects of introduced plants and animals on island vegetation: Examples from the Galápagos Archipelago. Conserv. Biol. 3, 227-238.
••  Somarriba, E. (1988) Guava (Psidium guajava L.) trees in a pasture: population model, sensitivity analyses, and applications. Agrofor. Syst. 6, 3-17. 
**# Ellshoff, Z.E., Gardner, D.E., Wikler, C. & Smith, C.W. (1996) Annotated bibliography of the genus Psidium, with emphasis on P. cattleianum (strawberry guava) and P. guajava (common guava), forest weeds in Hawai`i. Coop. Nat. Park Res. Stud. Unit  Techn. Rep. 95.
Pierre Binggeli 
May 1997

Schinus terebinthifolius Raddi (Anacardiaceae)
A South American tree introduced to Florida and Hawai'i for ornamental purposes. In Florida, it started to spread rapidly in the 1960s on abandoned agricultural land and is a threat to parts of the Everglades National Park.

Species characteristics
Life form, size, lifespan
Evergreen tree to 12 m with a broad canopy.
Taxonomy, variation and plasticity
Four varieties have been recognized.
Reproductive biology
Numerous white or yellowish flowers are born on panicles and are insect pollinated. In Florida flowers are pollinated by a native syrphid fly. The tree is dioecious. The drupe, when mature, is bright red and ca. 5 mm in diameter. In Florida robins (Turdus migratorius) are the main dispersal agent but introduced bird species also disperse the fruits. It produces fruits in its second year. Flowering occurs synchronously in October and fruits mature between December and January, although some reproductive activity may occur throughout the year.
Resilience and resistance
The species sprouts after fire and is resistant to salt-spray. It possesses mycorrhizal associations. It is thought to release allelopathic chemicals.
Environmental requirements and successional status
In abandoned farmland of Florida S. terebinthifolius is last species to become established in secondary succession and its stands are self-maintaining. Seedlings become established and survive both in open areas and under dense canopies.
Products and uses
Fruit-laden branches are used as Christmas decorations in both Hawai'i and Florida and the tree is sometimes known as the Christmas berry. It is an important winter ornamental in Florida.
Status in native range
Range and abundance
Native to Brazil, Paraguay and northern Argentina where it is sparsely distributed.
Climate
Dry tropical and sub-tropical regions of South America.
Site requirements 
Grows in a variety of habitats from coastal areas behind the mangrove fringe to around 700 m a.s.l. Favours disturbed habitats such as riverine forests.
Weediness
Not reported.
Pests and diseases
A number of insect species feeding on S. terebinthifolius have been recorded in Brazil.
Status in invaded regions
History of introductions and intensity of invasions
Introduced to Hawaii as an ornamental before 1900 and to Florida in 1989. In Florida it was first collected in the 1840s but was not widely planted until the 1920s and only became a conspicuous component of natural vegetation in the 1960s. It often forms monotypic stands.
Patterns of invasion and time-lag
In Florida S. terebinthifolius invades coastal and mesic prairies, pineland and particularly abandoned agricultural land where stem densities of up to 11355 stems ha-1 have been recorded. However, it is not found in areas were flooding lasts longer than 3-6 months. In pinelands S. terebinthifolius is largely excluded by fire when fire occurs in 3 to 7 year cycles. Successful establishment is lower in wetter areas probably as a result the elimination of and/or changes in the mycorrhizal associations. After the abandonment of farmland the S. terebinthifolius rate of spread increased dramatically as a result of soil improvement caused by increased nutrients and increased limestone pulverized from the bedrock during ploughing.
Site and climate
In Hawai'i it invades low-lying rangelands and waste grounds that receive a mean annual rainfall of 500 to 1150 mm. In Florida the rainfall is around 1600 mm with rains concentrated between May and October. Occasional winter frosts occur.
Floristic region and vegetation types
In Hawai'i it is found in coastal dry forest dominated by a mixture of exotics. The Everglades National Park contains a large number of tropical plants as well as 65 taxa endemic to southern Florida but is susceptible to invasive woody plants.
Pests and diseases
Cassytha filiformis, a parasitic climber native to Florida, has recently been found to significantly limit foliage production and reproductive capacity of S. terebinthifolius.
Impact on ecosystem
It alters successional patterns. In the Everglades, following farming that improves site quality, a forest community dominated by S. terebinthifolius replaces herbaceous plant communities. The intertwining crowns create dense shade resulting in little understorey herbaceous vegetation. This lack of vegetation and the limited leaf litter (leaves decompose rapidly) reduce fire susceptibility in mature stands. A number of wintering birds feed on the berries including introduced species.
Impact on humans and related activities
It has no forage value and where it forms dense canopies it shades out desirable forage grasses. Skin contact with leaves and the milky sap results in red, itching rashes and the tree's allergens also cause respiratory difficulties in many people. Profuse regeneration in suburban areas is not welcomed.
Control
Three insect species were introduced from Brazil to Hawaii in the 1950s to control S. terebinthifolius. By the mid 1960s the tree was only partially controlled on Hawai'i. On abandoned farmland infested by S. terebinthifolius, repeated burning does not retard or reduce the growth of mature trees but has some impact on smaller individuals. Fire is not considered as an appropriate management tool. Control using chemical and mechanical treatments, removal of substrate and particularly flooding has been used. Wetland restoration has been the most successful method used in controlling the spread of the species.
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
No native species appears to be able to take advantage of soil changes induced by past farming practices, particularly in relation to mycorrhizal associations. Under these conditions S. terebinthifolius clearly outcompetes native species. Its reproductive phenology differs markedly from native species with flowering in autumn and the production of ripe fruits in winter.
Differences in status and ecology between invaded and native ranges 
The introduction of insects for biological control suggest that the impact of insects on S. terebinthifolius populations is absent or negligible in the invaded range but has some impact in its native range.
Selected references 
# Barkley, F.A. (1944) Schinus L. Brittonia 5, 160‑198.
** Doren, R.F., Whiteaker, L.D. & LaRosa, A.M. (1991) Evaluation of fire as a management tool for controlling Schinus terebinthifolius as secondary successional growth on abandoned agricultural land. Environ. Mgmt 15, 121‑129.
* Ewel, J.J. (1984) Invasibility: lessons from South Florida. In Mooney, H.A. & Drake, J.A. (Eds) The ecology of biological invasions of North America and Hawaii, pp. 214‑230. Springer Verlag, New York.
* Goeden, R.D. (1978) Biological control of weeds. In Clausen, C.P. (Ed.) Introduced parasites and predators of arthropod pests and weeds: A world review, pp. 357‑414. Agricultural Handbook 480 USDA, Washington.
** Jones, D.T. (1997) The distribution, biology and control of Brazilian pepper (Schinus terebinthifolius Raddi) in southern Florida, with special reference to Everglades National Park. In Brock, J.H., Wade, M., Pysek, P. & Green, D. (Eds) Plant invasions: studies from North America and Europe, pp. 81‑93. Backhuys Publishers, Leiden.
** LaRosa, A.M., Doren, R.F. & Gunderson, L. (1992) Alien plant management in Everglades National Park: an historical perspective. In Stone, C.P., Smith, C.W. & Tunison, J.T. (Eds) Alien plant invasions in native ecosystems of Hawai'i: management and research, pp. 47‑63. University of Hawaii Press, Honolulu.
*# Morton, J.F. (1978) Brazilian pepper ‑ its impact on people, animals and the environment. Econ. Bot. 32, 353‑359. 
* Panetta, F.D. & McKee, J. (1997) Recruitment of the invasive ornamental, Schinus terebinthifolius, is dependent upon frugivores. Aust. J. Ecol. 22, 432‑438.
* Toops, C. (1979) Invaders of the Everglades. Am. For. 85(8), 38‑41, 50‑54.
* Wagner, W.L., Herbst, D.R. & Sohmer, S.H. (1990) Manual of flowering plants of Hawai'i. Bishop Museum and University of Hawaii Press, Honolulu.
Pierre Binggeli 
May 1997

Ulex europaeus L. (Papilionaceae)
Evergreen shrub from the Atlantic margin of Europe introduced to and spreading in many parts of the world. In the tropics it forms monotypic stands in mountainous areas subjected to large herbivore disturbance and/or fire.

Species characteristics
Life form, size, lifespan
Much-branched evergreen shrub to 2-4 m tall.
Taxonomy, variation and plasticity
In SW Britain U. europaeus hybridizes with U. galli Planch. where their flowering periods may overlap. It exhibits much intra- and inter- population variation in morphology. Leaves are present only at the seedling stage but thereafter are replaced by spines or scales.
Reproductive biology
The hermaphrodite yellow flowers are usually insect-pollinated and 1 to 3 of them are bone on axillary clusters. Pods (2 cm long) open explosively releasing 2 to 6 seeds and the seeds (6.2 mg, 3.3 x 2.3 mm) may be further dispersed by ants. Seeds can germinate after been subjected to temperature up to 88°C. A persistent seed bank is formed as some seeds remain viable for up to 28 years in the soil. In Britain flowering time varies from January to May according to latitude and set seeds two months later. Seed germination and seedling survival is lower under a U. europaeus canopy than in the open.
Resilience and resistance
When cut it coppices freely and following fire seed germination leads to high densities of seedlings. Shoot layering occurs. The species forms nitrogen-fixing root nodules. Its rooting system is shallow with a deep tap root.
Environmental requirements and successional status
Seedlings are often found at sites with some bare ground. Its nitrogen fixing capacity allow growth under conditions of extreme infertility. The shrub is light demanding and dies through shading but seedlings may become established under its own canopy. Bushes start degenerating after 20 years unless fire occurs.
Products and uses
It has potential for land reclamation and has been used as a hedge plant and for binding soil on dry sandy banks. On marginal land it is a source of food for cattle and ponies and formerly, after removal of spines, it was used for fodder.
Status in native range
Range and abundance
Extensively distributed in the Atlantic part of Europe. Scattered throughout central Europe where it is thought to be naturalised. Rarely found in forests apart from forest edges. May form monotypic stands in disturbed areas.
Climate
Temperate oceanic climate with mild winters and mild to cool summers.
Site requirements 
Requires disturbance, such as fire or large grazing herbivores, for establishment. Absent from arable and wetland habitats.
Weediness
Very common in disturbed habits such as wasteland, river banks, quarry spoils, roadsides and railway embankments. Has increased since the 1950s after myxomatosis dramatically reduced rabbit populations.
Pests and diseases
A large number of insects have found feeding on the shrub, but at very low densities.
Status in invaded regions
History of introductions and intensity of invasions
Introduced to many montane regions of the tropics, including Peru, La Réunion, Sri Lanka, St Helena and Hawai'i. U. europaeus is now naturalized in Sri Lanka and is considered a serious pest on two Hawaiian Islands. It was inadvertently introduced prior to 1910 when the wool industry was established. The species was introduced to many temperate regions and is a serious pests. In La Réunion it has extensively invaded heathlands, particularly in areas disturbed by cultivation and grazing. It forms monotypic stands in South America including in areas previously forested. Invasive in many temperate areas were the plant was often used as hedge material.
Patterns of invasion and time-lag
U. europaeus forms impenetrable and often extensive thickets with as many as 60,000 stems/ha. Its poor long-distance dispersal ability ensures that few distant founder populations are started. During the 1930s Hawaiian ranchers converted to cattle ranching and U. europaeus, until then controlled by sheep grazing, began to increase. Microsites produced by the hooves of large herbivores are ideal for gorse seedling establishment, gorse being a poor competitor. Drought and associated removal of grazing pressure appear to have contributed to the infestations.
Site and climate
It grows as low as 460 m a.s.l. but most of its distribution is between 630 and 2220 m. In South America the shrub is found up to 3200 m.
Floristic region and vegetation types
Range land vegetation often on site of former forests.
Pests and diseases
Not reported but presumably are few and have no significant effect.
Impact on ecosystem
In La Réunion it is said that U. europaeus has a higher combustible biomass and is probably more flammable than the native vegetation. In some parts New Zealand it has been suggested that stands of U. europaeus facilitate the regeneration of native forest trees. Its presence results in some soil acidification.
Impact on humans and related activities
U. europaeus represents a fire hazard to private property. It invades watersheds which supply a substantial amount of drinking water. It is threatening agricultural and grazing lands. Thickets are impenetrable to humans and have persistent spiny litter.
Control
In Hawaii, temporary control was undertaken in the 1970s using 2,4-5 T. The ban of the herbicide and lack of funding ended the programme. A task force was later set up to coordinate a management approach which included the following four control programmes: a/ containment: using Tordon 22K strips along roadsides were first targeted to eliminate the possibility of seed transport to new areas, b/ long-term biological: search for control agents in Europe which in 1984 resulted in the release of a seed weevil (Apion ulicis Forster). The weevil is now well established and spreading, but despite destroying 50% of seeds it had no detectable impact on the spreading populations c/ reforestation: using mainly native trees to shade out U. europaeus and d/ grazing: use of goats (Capra hircus) after fire. 
Ecological differences 
Existence of ecological equivalent species and competitive interactions in invaded regions
No clear evidence is available but it appears that no equivalent species occur in any of the tropical regions invaded.
Differences in status and ecology between invaded and native ranges 
Unusual case of a species with a temperate Atlantic distribution invading mountainous tropical regions as well as other temperate regions. However in all reported cases both in native and invaded ranges U. europaeus regeneration is highly favoured by the production of microsites by large hoofed mammals, particularly cattle. Differences in seedbank have been found between temperate regions.
Selected references 
* Cadet, T. (1974) Etude sur la végétation des hautes altitudes de La Réunion (Océan Indien). Vegetatio 29, 121-130.
* Cronk, Q.C.B. (1989) The past and present vegetation of St Helena. J. Biogeogr. 16, 47-64.
* Figier, J. & Soulères, O. (1991) Le problème des exotiques envahissantes à la Réunion. Bois Foret Trop. 229, 31-34.
# Gaynor, D.L. & MacCarter, L.E. (1981) Biology, ecology and control of gorse (Ulex europaeus L.): a bibliography. N.Z. J. agric. Res. 24, 123-137.
•• Grime, J.P., Hodgson, J.G. & Hunt, R. (1988) Comparative plant ecology. Unwin Hyman, London.
• Hill, R.L. (1982) The phytophagous fauna of gorse (Ulex europaeus L.) and host plant quality. Ph.D. thesis, University of London.
# Holm, L., Doll, J., Holm, E., Pancho, J. & Herberger, J. (1997) World weeds: natural histories and distributions. Wiley, New York.
* Markin, G.P., Yoshioka, E.R. & Conant, P. (1996) Biological control of gorse in Hawaii. In Moran, V.C. & Hoffman, J.H. (Eds) Proceedings of the 9th international symposium on biological control of weeds, pp. 371-375. University of Cape Town, Rondebosch.
• Millener, L.H. (1952) Experimental studies on the growth forms of the British species of Ulex. Ph.D. thesis, University of Cambridge.
• Tubbs, C.R. & Jones, E.L. (1964) The distribution of gorse (Ulex europaeus L.) in the New Forest in relation to former land use. Proc. Hampshire Fld Club 23, 1-10.
** Tulang, M. (1992) The U.S. Department of Agriculture's rural development approach to alien plant control in Hawai'i: a case study. In Stone, C.P., Smith, C.W. & Tunison, J.T. (Eds) Alien plant invasions in native ecosystems of Hawai'i: management and research, pp. 577-583. University of Hawaii Press, Honolulu.
Pierre Binggeli 
May 1997