A rapid survey of the invasive plant species in western Angola

Abstract

Angola is one of the most neglected African countries in terms of botanical research, in respect of both native and naturalized species. We conducted a rapid assessment of invasive plant species in western Angola during August 2014. In thirteen primary vegetation types, we recorded populations of 44 naturalized plant species, nineteen of which are conclusively invasive (spreading far from introduction sites). Dense invasive populations of Chromolaena odorata, Inga vera and Opuntia stricta pose the greatest environmental and economic threats. Some species with known taxonomic and/or biogeographic uncertainties (e.g. Chromolaena odorata and Ageratina adenophora) or which lacked key characteristics for identification such as flowers during our survey (e.g. Eucalyptus spp.) were subjected to DNA barcoding for comparisons with available genetic data from other studies. This approach allowed us to confirm the identity of taxonomically challenging taxa such as Inga vera, Opuntia stricta and Prosopis chilensis, to conclusively differentiate Chromolaena odorata from Ageratina adenophora, and identify the subspecific identity of Acacia saligna. Canonical correspondence analysis was used to assess the presence and abundance of invasive plant species with respect to the major abiotic factors and vegetation types. Three fairly distinct groups of species emerge from this analysis: (i) species of dry lowland habitats (Calotropis gigantea, Leucaena leucocephala and Opuntia stricta); (ii) species of relatively wet habitats at mid elevations (Ageratum conyzoides, Bidens pilosa, Cardiospermum grandiflorum, Chromolaena odorata, Solanum mauritianum and Tithonia diversifolia); and (iii) upland species (Ageratina adenophora, Galinsoga parviflora and Tagetes minuta). Several invasive species that are widespread in other tropical and subtropical African countries are currently either missing (e.g. many Australian Acacia species, Azolla filiculoides, Broussonetia papyrifera, Clidemia hirta, Parthenium hysterophorus, Rubus rosaefolius, Salvinia molesta), have only very localized populations in Angola (e.g. Lantana camara, Prosopis chilensis) or exist only as planted individuals (e.g. Acacia mearnsii and A. saligna subsp. saligna).

Contrasting impacts of an alien invasive shrub on mammalian savanna herbivores revealed on a landscape scale

“…But we did show that the large‐scale clearing programme has led to species restoring their habitat use and this may have come in time to prevent population‐level effects on some of the species that responded in terms of habitat selection. This example from Hluhluwe‐iMfolozi Park could serve as an example for protected areas elsewhere where the invasion of C. odorata or other high‐impact invaders, such as Lantana camara L. or Parthenium hysterophorus L. is in its early stages and/or not currently managed (Beale et al., ; Rejmánek, Huntley, Le Roux, & Richardson, ).…”

A brief botanical survey into Kumbira forest, an isolated patch of Guineo-Congolian biome

“…The exotic, evergreen Inga trees ( Inga vera from northern South America) planted initially as shade for the coffee are now overgrown and let little light through the canopy, seriously reducing the development of a shrub or herb layer except in gaps. Inga vera was recently referred as one of the most impressive and worrying invasive species of western Angola, forming dense stands in localized sites as observed in Kumbira forest (Rajmánek et al 2016). Nevertheless, we did record a variety of ferns and other herbaceous plants in this area, in addition to the very large fig Ficus saussureana , the first record of this Guineo-Congolian species from Angola.…”

Biodiversity Conservation: History, Protected Areas and Hotspots

“…Invasive alien plants have already become established over extensive areas of western Angola. Rejmánek et al (2017) conducted a rapid assessment of invasive plant species across 13 primary vegetation types (Barbosa 1970) in western Angola and recorded populations of 44 naturalised plant species, 19 of which are conclusively invasive (spreading far from introduction sites). They found that dense invasive populations of Chromolaena odorata, Inga vera and Opuntia stricta pose the greatest threats.…”