An assessment of the distribution and potential ecological impacts of invasive alien plant species in eastern Africa

Figures & data

Figure 1. Location of five countries in East Africa in which surveys were undertaken to record the presence of alien plant species.

Figure 2. Grid cells (approximately 55 km × 55 km) within five countries in East Africa that were surveyed for the presence of alien plant species between 2008 and 2016.

Table 1. The total number of grid cells (approximately 55 km × 55 km) in five eastern African countries, and the number of grid cells included in surveys of invasive alien plant species.

Country	Total number of grid cells	Number of grid cells surveyed	% of country and region surveyed
Ethiopia	416	145	34.9
Kenya	201	129	64.0
Rwanda	13	12	93.3
Tanzania	344	169	49.1
Uganda	90	67	74.4
Total	1063	522	49.1

Table 2. Invasive species with an uncertain or disputed origin¹ and problematic native species² (sometimes referred to as extra-limital or range extension species) in Ethiopia (ET), Kenya (KE), Rwanda (RW), Tanzania (TZ) and Uganda (UG), with brief notes on habitat types invaded (Fo, forest; Sa, savanna; Gr, grassland; Tr, transformed; Rr, road/railside; Ha, around habitation; Pl, plantation; Ar, arable/ploughed land; Pa, pastoral; Ws, wasteland; Wc, watercourse; Wt, wetland; Dr, dryland/well drained; Kl, kloof/ravine; Ro, rocky site), and impacts. A full set of references to accounts of impact are contained in Witt and Luke (2017).

Species and family	Growth form and invasive type	Distribution			Habitat types invaded	Impact
		Countries invasive	% of surveyed grid cells present	% of surveyed grid cells abundant or invasive
Calotropis procera (Aiton) Dryand (Apocynaceae)^1	Tree or shrub	ET, KE, RW?, TZ, UG	34.1	19.4	Tr, Rr, Ha, Ar, Pa, Ws	Forms large and dense thickets, especially along roadsides and in low-lying areas, displacing native species. Plant sap can cause severe irritation if it comes into contact with the eyes. Ingestion by livestock is suspected of causing ill-health and sometimes even death.
Pistia stratiotes L. (Araceae)^1	Aquatic	ET, KE, RW, TZ, UG	7.5	5.1	Wc, Wt	Invasions cause increased rates of siltation, slow water flow rates, degrade fish nesting sites, increase nutrient loading, and increase fish and macro-invertebrate mortality. Invasions block waterways, hamper fishing activities, interfere with hydroelectricity generation and provide habitats for vectors of disease.
Ipomoea cairica (L.) Sweet (Convolvulaceae)^2	Climber	ET, KE, RW, TZ, UG	15.1	4.1	Sa, Rr, Ha, Ws, Wc	Climbs into and over trees and shrubs, smothering them, to the detriment of native flora and fauna. In southern China, where it is listed as one of the worst invasive species, invasions significantly decreased plant richness and diversity. In New South Wales, Australia, remnant communities of endangered plants are thought to be under threat from this species.
Ipomoea hildebrandtii Vatke (Convolvulaceae)^2	Shrub	ET, KE, TZ	6.2	4.5	Sa, Gr, Pa	Extremely abundant on some rangelands in eastern Africa, possibly as a result of overgrazing and absence of fires. Decreases grass biomass and livestock productivity.
Ricinis communis (Euphorbiaceae)^1	Shrub	ET, KE, RW, TZ, UG	66.7	41.1	Sa, Tr, Ws, Wc	Forms dense stands which displace native vegetation, especially in riparian areas and along drainage lines. The plant is toxic, especially the seeds.
Senna didymobotrya (Fresen.) H.S. Irwin & Barneby (Fabaceae)^2	Tree or shrub	ET, KE, RW, TZ, UG	37.5	19.0	Sa, Tr, Ha, Ws	Has the ability to form large, dense mono-specific stands, displacing native plant species and inhibiting wildlife movement.
Tephrosia vogelli Hook. f. (Fabaceae)^1	Shrub or tree	ET, KE, RW, TZ, UG	5.3	0.4	Sa, Ar	Is allelopathic and its leaves are highly toxic to frogs, toads, molluscs, worms and insects, including fish. Also an alternate host for the groundnut plant hopper.
Myriophyllum spicatum L. (Haloragaceae)^1	Aquatic	ET, KE	Not actively recorded during surveys		Wc, Wt	Interferes with irrigation flows, hampers water transport, hydro-electric generation, fisheries and recreation, while increasing the risk of flooding. Reduces the abundance of waterfowl and other animals that depend on native aquatic species, and the abundance of invertebrates, and make it more difficult for fish to forage.
Solanum campylacanthum Hochst. ex A. Rich. (Solanaceae)^2	Shrub	ET, KE, RW, TZ, UG	55.2	46.0	Sa, Gr, Tr, Rr, Ha, Ar, Pa, Ws	Forms dense stands, reducing native plant abundance and diversity. Unripe fruits are toxic to livestock, especially sheep.

Figure 3. The growth forms of 164 invasive alien species in eastern Africa.

Figure 4. Date of first records of introduced plant species now considered to be invasive in eastern Africa.

Table 3. Families with four or more invasive alien species in eastern Africa

Family	No. of invasive alien species	Percentage (%)
Fabaceae	27	16
Asteraceae	17	10
Solanaceae	13	8
Cactaceae	9	5
Apocynaceae	6	4
Convolvulaceae	6	4
Commelinaceae	5	3
Passifloraceae	5	3
Verbenaceae	5	3
Agavaceae	4	2
Crassulaceae	4	2
Euphorbiaceae	4	2
Meliaceae	4	2
Myrtaceae	4	2

Table 4. Cultivated uses of invasive alien species recorded in eastern Africa. Species may have been allocated to more than one category.

Cultivated use	No. of species	Percentage (%)
Ornamental	146	46
Barrier/hedge	48	15
Agricultural crop	47	15
Domestic	31	10
Medicinal	17	5
Silvicultural crop	16	5
Cover/binder	8	3
No recorded uses	7	2

Table 5. The distribution of what we consider to be the 30 species with the greatest impact in terms of transforming natural vegetation in Ethiopia (ET), Kenya (KE), Rwanda (RW), Tanzania (TZ) and Uganda (UG), with brief notes on habitat types invaded (Fo, forest; Sa, savanna; Gr, grassland; Tr, transformed; Rr, road/rail side; Ha, around habitation; Pl, plantation; Ar, arable/ploughed land; Pa, pastoral; Ws, wasteland; Wc, watercourse; Wt, wetland; Dr, dryland/well drained; Kl, kloof/ravine; Ro, rocky site), and impacts. A full set of references to accounts of impact are contained in Witt and Luke (2017).

Species and family	Growth form and invasive type	Distribution			Habitat types invaded	Negative impacts
		Countries invasive	% of surveyed grid cells present	% of surveyed grid cells invasive
Agave angustifolia Haw. (Agavaceae)	Succulent shrub	KE, RW, TZ	17.1	4.3	Sa, Tr, Rr, Ha, Pa, Ws, Dr	Out-competes and displaces native plants in semi-arid environments, through more efficient exploitation of water and nutrients.
Cascabela thevetia (L.) Lippold (Syn: Thevetia peruviana (Pers.) K. Schum (Apocynaceae)	Tree or shrub	KE, TZ, UG	48.6	6.0	Sa, Tr, Ha, Pa, Wc	Forms dense thickets, especially in low-lying areas and along watercourses, displacing native plant and animal species. Extremely toxic.
Chromolaena odorata (L.) R.M. King & H. Rob. (Asteraceae)	Shrub	KE, TZ, UG	1.9	1.5	Sa, Tr, Rr, Ha, Ar, Pa, Ws, Wc	Displaces native plant species, and alters fuel properties of vegetation, increasing fire intensities. Reduces the productivity of rangelands, and can cause serious health problems in livestock and people.
Parthenium hysterophorus L. (Asteraceae)	Herb	ET, KE, RW, TZ, UG	31.6	25,4	Sa, Gr, Tr, Rr, Ha, Ar, Pa, Ws, Wc	Allelopathic and able to suppress natural vegetation. Severely reduces the productivity of rangelands, and causes serious allergenic reactions (dermatitis, hay fever and asthma) in a large proportion of people who come into contact with it, as well as in livestock and wildlife.
Tithonia diversifolia (Hemsl.) A. Gray (Asteraceae)	Shrub	KE, RW, TZ, UG	29.4	23.5	Sa, Tr, Rr, Ha, Pl, Ar, Pa, Ws, Wc	Displaces native vegetation and reduces species diversity and the productivity of rangelands. Contributes to the local extinction of valued native species.
Xanthium strumarium L. (Asteraceae)	Herb	ET, KE, RW, TZ, UG	34.1	28.4	Sa, Tr, Rr, Ar, Ws, Wc	Rapidly forms large stands, displacing other plant species. Toxic to livestock and can lead to death if eaten.
Austrocylindropuntia subulata (Muelenpf.) Backeb. (Cactaceae)	Succulent tree or shrub	KE, TZ, UG	12.1	4.0	Sa, Rr, Ha, Pa, Wc, Dr	Forms impenetrable thickets that prevent access to grazing pastures and water resources. Infestations reduce the livestock-carrying capacities of pastures. The spines cause injuries to livestock, wildlife and people.
Opuntia stricta (Haw.) Haw. (Cactaceae)	Succulent tree or shrub	ET, KE, TZ	9.8	5.1	Sa, Rr, Ha, Pa, Ws, Wc, Dr, Ro	Substantially reduces livestock carrying capacities and reduces access to grazing and water resources. When eaten, causes infections, injury and mortality in livestock.
Bryophyllum delagoense (Eckl. & Zeyh.) Druce (Crassulaceae)	Succulent herb	ET, KE, UG	5.2	2.5	Sa, Tr, Rr, Ha, Pa, Ws, Wc	Forms dense monotypic stands, which displace native plant species. Toxic to livestock and humans and probably also to wildlife.
Acacia mearnsii De Wild (Fabaceae)	Tree or shrub	ET, KE, RW, TZ, UG?	15.4	6.4	Fo, Gr, Tr, Rr, Ha, Pl, Ws, Wc	Displaces natural vegetation, reducing native biodiversity and rangeland productivity. Reduces surface water runoff. Increases soil nitrogen levels, altering soil nutrient cycling.
Acacia melanoxylon R. Br (Fabaceae)	Tree or shrub	KE, TZ, RW?	5.6	1.7	Fo, Gr, Tr, Rr, Ha, Pl, Ws, Wc	Displaces native vegetation in forests and riparian zones, with negative impacts on biodiversity. Increases soil nitrogen levels, altering soil nutrient cycling.
Acacia saligna Wendl (Fabaceae)	Tree or shrub	ET	8.5	1.3	Sa, Tr, Rr, Pa, Ws	Forms dense, impenetrable thickets, which displace native species and prevent their regeneration. Reduces surface water runoff. Increases soil nitrogen levels, altering soil nutrient cycling.
Caesalpinia decapetala (Roth) Alston (Fabaceae)	Climber	ET, KE, RW, TZ, UG	35.6	12.6	Fo, Sa, TR, Rr, Ha, Pl, Pa, Ws, Wc	Climbs over vegetation, forming tangled, impenetrable thickets, detrimental to fauna and flora. Grows into forest and woodland canopies, causing canopy collapse. Impedes forest management operations and is a fire hazard. Reduces livestock-carrying capacities and inhibits the movement of livestock and people. The large spines on the stems can cause injuries to wildlife, livestock and people.
Leucaena leucocephala (Lam.) de Wit (Fabaceae)	Tree or shrub	ET, KE, RW, TZ, UG	53.9	15.4	Sa, Tr, Rr, Ha, Pa, Ws, Wc	Forms large monocultures, displacing native plant and animal species. Invasions alter secondary succession processes and render areas unusable and inaccessible.
Mimosa diplotricha Sauvalle (Fabaceae)	Tree or shrub	ET, RW, TZ, UG	3.2	3.0	Fo, Sa, Gr, Tr, Rr, Ha, Pl, Ar, Pa, Ws, Wc	Smothers other plants, shading out light-demanding species and preventing their natural regeneration. Dense stands may prevent or inhibit the movement of livestock and wildlife. Evidence suggests that it is toxic to both sheep and pigs.
Mimosa pigra L. (Fabaceae)	Tree or shrub	ET, KE, RW, TZ, UG	15.1	11.7	Sa, Tr, Rr, Ha, Ar, Pa, Ws, Wc, Wt	Dense infestations can eliminate native plant and animal species, and lead to steep declines in the abundance of others. Hampers fishing activities, and blocks access to water bodies.
Prosopis juliflora (Sw.) DC. (Fabaceae)	Tree or shrub	ET, KE, TZ	26.0	9.8	Sa, Tr, Rr, Ha, Ar, Pa, Ws, Wc	Reduces grazing capacity, eliminates many species from invaded ecosystems and depletes groundwater resources. Despite some benefits in the form of firewood and edible pods, the overall net economic contribution is negative, and set to worsen as the species continues to spread.
Senna spectabilis (DC.) H.S. Irwin & Barneby (Fabaceae)	Tree or shrub	KE, TZ, UG	36.0	4.5	Fo, Tr, Rr, Ha, Ws, Wc	Grows rapidly, dominating other species and displacing native flora and fauna. Inhibits regeneration of native plant species.
Clidemia hirta (L.) D. Don (Melastomataceae)	Tree or shrub	KE, TZ	0.6	0.6	Fo, Tr, Rr, Pl, Ws, Wc	Forms dense stands, displacing native vegetation and threatening endemic plant species. Toxic to livestock.
Azadirachta indica A. Juss. (Meliaceae)	Tree or shrub	ET, KE, TZ	49	7.3	Fo, Sa, Tr, Rr, Ha, Pl, Pa, Ws	Forms dense stands, especially in coastal areas, displacing native plant species. Alters habitats, leading to reductions in the abundance of small mammals.
Psidium guajava L. (Myrtaceae)	Tree or shrub	ET, KE, RW, TZ, UG	42.0	9.8	Fo, Sa, Tr, Rr, Ha, Pl, Pa, Ws, Wc	Establishes dense stands, displacing native plant and animal species. Allelopathic, impacting negatively on some crop species. Can be invasive in secondary forests.
Passiflora subpeltata L. (Passifloraceae)	Climber	KE	1.3	0.9	Fo, Sa, Tr, Rr, Ha, Pl, Ws, Wc	Climbs into and over vegetation, smothering native plants and reducing plant diversity. Thought to be toxic to humans and livestock.
Pinus patula Schiede ex Schltdl. & Cham. (Pinaceae)	Tree or shrub	KE, TZ	7.3	0.9	Fo, Gr, Tr, Rr, Ha, Pl, Pa, Ws, Wc	Forms dense stands, displacing native plant and animal species and reducing water run-off. Considered to be one of the most aggressive invaders of afro-montane forests and grasslands.
Eichhornia crassipes (Mart.) Solms (Pontederiaceae)	Aquatic	ET, KE, RW, TZ, UG	5.6	4.3	Wc, Wt	Forms thick mats which hamper water transport; inhibit or prevent fishing-related activities; blocks waterways; hampers hydroelectricity generation; and provides habitats for vectors of human and animal diseases.
Rubus niveus Thunb. (Rosaceae)	Climber or shrub	KE, TZ	1.5	0.9	Fo, Tr, Rr, Pl, Ws, Kl	Forms dense, thorny thickets, which out-compete and displace native vegetation, inhibiting the regeneration of native species and threatening rare plants. Alters the structure and condition of ecosystems.
Cestrum aurantiacum Lindl. (Solanaceae)	Tree or shrub	KE	3.6	0.8	Fo, Sa, Tr, Rr, Ha, Pl, Pa, Ws, Wc	Cimbs into trees and over shrubs, smothering native vegetation. Toxic to people and to livestock.
Datura stramonium L. (Solanaceae)	Herb	ET, KE, RW, TZ, UG	45.2	34.1	Sa, Gr, Tr, Rr, Ha, Ar, Pa, Ws	Competes aggressively with native plants and crops, forming dense monospecific stands. Toxic to people and animals.
Solanum mauritianum Scop. (Solanaceae)	Tree or shrub	KE, RW, UG	10.4	5.5	Fo, Tr, Rr, Ha, Pl, Ws, Wc	Displaces native plant and animal species. By producing copious amounts of edible seeds, it disrupts natural seed dispersal mechanisms, leading to declines in affected native plant species. The plant, if consumed, is toxic to livestock.
Lantana camara L. (Verbenaceae)	Tree or shrub	ET, KE, RW, TZ, UG	54.4	38	Fo, Sa, Gr, Tr, Rr, Ha, Pl, Ar, Pa, Ws, Wc	Displaces natural vegetation, impacting negatively on biodiversity. Toxic to livestock, causing animal deaths, reduced productivity, and loss of pasture.

Table 6. Details on the invasive alien plant species considered to be potential transformers of natural vegetation in Ethiopia (ET), Kenya (KE), Rwanda (RW), Tanzania (TZ) and Uganda (UG), with brief notes on habitat types invaded (Fo, forest; Sa, savanna; Gr, grassland; Tr, transformed; Rr, road/railside; Ha, around habitation; Pl, plantation; Ar, arable/ploughed land; Pa, pastoral; Ws, wasteland; Wc, watercourse; Wt, wetland; Dr, dryland/well drained; Kl, kloof/ravine; Ro, rocky site), and impacts. A full set of references to accounts of impact are contained in Witt and Luke (2017).

Species and family	Growth form and invasive type	Distribution			Habitat types invaded	Impact
		Countries invasive	% of surveyed grid cells present	% of surveyed grid cells invasive
Thunbergia grandiflora Roxb. (Acanthaceae)	Climber	TZ, UG	1.7	0.4	Fo, Ha, Pl, Wc	Smothers established plants and prevents the regeneration of native species in invaded areas. Heavy and extensive root system can destabilise riverbanks and foundations.
Cryptostegia grandiflora Roxb. ex R. Br (Apocyncaeae)	Tree or shrub	ET	2.4	0.6	Sa, Tr, Pa, Wa, Dr	Climbs into trees, smothering native vegetation and causing canopy collapse, to the detriment of native plant and animal species. Dense invasions can reduce livestock carrying capacities by as much as 100%. Plant is toxic to humans and animals.
Dahlia imperialis Roezl ex Ortgies (Asteraceae)	Herb	KE, TZ	2.6	0.9	Fo, Rr, Ha, Pl, Ar, Ws	Forms dense stands which may displace native fauna and flora. Invasions in plantation increase management costs. Considered to be toxic.
Montanoa hibiscifolia Benth. (Asteraceae)	Shrub	TZ	1.3	0.4	Fo, Sa, Tr, Rr, Ha, Ws, Wc	Forms dense monospecific stands, probably displacing native plant and animal species.
Senecio madagascariensis Poir. (Asteraceae)	Herb	KE	0.9	0.8	Sa, Gr, Rr, Ha, Pa, Ws	Forms dense stands displacing valuable forage species and as such reducing pasture-carrying capacities. Is also toxic to livestock.
Tithonia rotundifolia (Mill.) S.F. Blake (Asteraceae)	Tree or shrub	KE, TZ, UG	5.1	1.7	Sa, Tr, Rr, Ha, Ar, Ws	Has the ability to form dense stands to the detriment of native flora and fauna and as such considered to alter ecosystem services.
Anredera cordifolia (Ten.) Steenis. (Basellaceae)	Climber	KE	2.6	0.6	Fo, Rr, Pl, Ws, Wc, Kl	Smothers native vegetation, including trees, causing canopy collapse. Aerial tubers can remain viable on the ground for two years, making management difficult. Toxic to pigs, sheep and possibly cattle and goats.
Dolichandra unguis-cati (L.) L.G. Lohmann (Bignoniaceae)	Climber	KE, TZ	0.8	0.4	Fo, Rr, Ha, Pl, Ws, Wc	Climbs into trees and forest canopies, smothering plants and causing canopy collapse. Displaces understorey plants and prevents their regeneration.
Tecoma stans (L.) Juss. ex Kunth (Bignoniaceae)	Tree or shrub	ET, KE, TZ	26.2	2.8	Sa, Rr, Ha, Pa, Ws, Wc	Forms dense stands which may result in the displacement of native species. Invasions have led to the abandonment of productive land in Brazil.
Opuntia elatior Mill. (Cactaceae)	Succulent tree or shrub	KE	1.1	1.1	Sa, Tr, Rr, Ha, Pa, Ws, Dr	Forms dense, impenetrable thickets, reducing access to available forage and to other natural resources such as water. Consumption of the fruit by livestock may result in impacts of the kind recorded for Opuntia stricta.
Opuntia engelmannii Salm-Dyck ex Engelm. (Cactaceae)	Succulent tree or shrub	KE	0.6	0.2	Sa, Tr, Rr, Ha, Pa, Ws, Dr	Forms dense thickets, displacing native plant and animal species. Grasses and other forage species growing around the plants are not consumed due to cactus spines. Reduces livestock carrying capacities, and deprives wildlife of habitat. Consumption of the fruits by livestock may result in impacts of the kind recorded for Opuntia stricta.
Pereskia aculeata Mill. (Cactaceae)	Climber	KE, UG	0.4	0.4	Fo, Rr, Ha, Pl	Climbs into trees and over shrubs, smothering plants and forming dense, impenetrable thickets, to the detriment of native plants and animals.
Acacia colei Maslin & L.A.J.Thomson (Fabaceae)	Tree or shrub	KE, TZ	3.8	2.3	Sa, Rr, Ha, Ar, Pa, Dr	Potentially harmful (as for other Australian Acacia species) but impacts not documented.
Calliandra houstoniana (Mill.) Standl. var. calothyrsus (Meisn.) Barneby (Fabaceae)	Tree or shrub	KE, RW, TZ, UG	9.4	2.4	Sa, Tr, Rr, Ha, Ws, Wc, Kl	Forms dense thickets, displacing native species, especially in riparian areas. Highly adaptable and is able to grow under a wide range of soil and environmental conditions.
Hyptis suaveolens (L.) Poit. (Lamiaceae)	Herb	ET, KE, TZ	0.8	0.8	Sa, Tr, Rr, Ha, Ar, Pa, Ws	Forms dense stands, to the detriment of native fauna and flora. Regarded as one of the worst weeds in the world.
Broussonetia papyrifera (L.) L’Her.ex Vent. (Moraceae)	Tree or shrub	UG	0.8	0.6	Fo, Rr, Ha, Pl, Ws	Forms dense stands which displace native plant species, prevent forest regeneration, and reduce water availability. Produces vast quantities of allergenic pollen.
Passiflora suberosa L. (Passifloraceae)	Climber	KE, TZ	0.9	0.4	Fo, Ha, Pl, Ws, Wc	Smothers native vegetation, reducing biodiversity. Areas covered with dead and dying native plants become a fire hazard. May be toxic.
Antigonon leptopus Hook. & Arn. (Polygonaceae)	Climber	KE, TZ	3.0	0.9	Fo, Tr, Rr, Ha, Ws, Wc	Smothers native trees, out-competes understorey plants, and alters fire regimes. Abundant on coastal dunes and forests.
Cardiospermum grandiflorum Sw. (Sapindaceae)	Climber	KE, UG	3.0	0.9	Fo, Tr, Rr, Ha, Pl, Ws, Wc	Climbs onto trees and shrubs causing canopy collapse, especially along forest edges and watercourses and in urban open spaces. Capable of smothering trees up to 10  m tall.
Hedychium coronarium J.Koenig (Zingiberaceae)	Herb	KE	0.6	0.2	Fo, Ha, Wc, Wt	Forms extensive thickets that disrupt water flow in channels and displace and suppress the regeneration of native wetland plants. Toxic.
Hedychium flavescens Carey ex Roscoe (Zingiberaceae)	Herb	KE	0.2	0.2	Fo, Ha, Wc, Wt	Forms dense monospecific stands, to the detriment of native flora and fauna; prevents the establishment of other plant species. Alters nutrient levels and hydrological processes, and impedes access.

Table 7. Naturalised species of plants in the East Usambara mountains, Tanzania, as recorded by Sheil (1994).

Species	Family	Origin
Adiantum raddianum C. Presl.	Adiantaceae	Tropical America
Albizia chinensis (Osbeck) Merr.	Fabaceae	Tropical Asia
Milletia dura Dunn	Fabaceae	Tropical Africa
Axonopus compressus (Sw.) Beauv.	Poaceae	Tropical America
Olyra latijolia L.	Poaceae	Tropical Africa
Coffea arabica L.	Rubiaceae	Tropical Africa
Dioscorea alata L.	Dioscoreaceae	Tropical Asia
D. bulbifera L. var. anthropophagorum (A. Chev.) Summerh	Dioscoreaceae	Tropical Asia
Drymaria cordata (L.) Rom. & Schultes	Caryophyllaceae	Tropical America
Elettaria cardamomum (L). Maton	Zingiberaceae	Tropical Asia
Ficus altissima Blume	Moraceae	Tropical Asia
Fuchsia arborescens Sims	Onagraceae	Tropical America
Lantana trifolia L.	Verbenaceae	Tropical America
Stachytarpheta urticifolia Sims	Verbenaceae	Tropical America
Ipomoea lobata (Cerv.) Thell.	Convolvulaceae	Tropical America
Nephrolepis cordifolia (L.) C. Presl.	Nephrolepidaceae	Tropical Australia
N. occidentalis Kunze	Nephrolepidaceae	Tropical Australia
Sagittaria montevidenis Cham. & Schlechtd.	Alismataceae	North Temperate America
Selaginella biformis Kuhn	Selaginellaceae	Tropical Asia
S. perpusilla Bak.	Selaginellaceae	Tropical Asia
S. plana (Dew.) Hieron.	Selaginellaceae	Tropical Asia
Podocarpus latifolius (Thunb.) R.Br. ex Mirb.	Podocarpaceae	South Temperate Africa

Witt, A.B.R. & Luke, Q. 2017. Guide to the Naturalized and Invasive Plants of Eastern Africa. Wallingford, CAB International.

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Sheil, D. 1994. Invasive plants in tropical forests: Warnings from the Amani Botanic Gardens, Tanzania. Botanical Gardens Conservation News 2(3): 23–24.

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