Open Access

Luca Afonso, Karen J. Esler, Mirijam Gaertner, Sjirk Geerts

• Urban areas are considered hotspots for invasions by alien plant communities. Anthropogenic activity within these areas often facilitates the introduction and spread of invasive alien plants, withUrban areas are considered hotspots for invasions by alien plant communities. Anthropogenic activity within these areas often facilitates the introduction and spread of invasive alien plants, with urban gardens acting as a significant source of propagules. This makes natural areas within and surrounding urban areas particularly vulnerable to invasion by alien plants. The city of Cape Town, South Africa, provides an ideal opportunity to study plant invasions at the urban/wildland interface since urban and suburban areas contain a mosaic of natural areas embedded within the urban fabric. We hypothesized that invasive alien plant species richness and abundance would be significantly higher in urban areas and peri-urban areas compared to rural areas. We sampled plant species richness and abundance in 15 sites – from the Cape Town Biological Network – across the urban-wildland interface (urban, peri-urban and rural). Plant species were grouped according to invasion pathways and adaptive strategies. There was no significant difference in invasive alien plant abundance between urban and rural habitat types, but invasive alien plant abundance was significantly higher in peri-urban habitat types compared to urban and rural habitat types. Species richness was similar between urban, rural and peri-urban habitats. There were equal proportions of competitors and ruderal species in urban areas, but a higher proportion of ruderal species in both the peri-urban and rural habitat types. Agricultural invasive alien plant species were more common throughout, compared to species originating from horticulture or forestry. To secure healthy ecological networks with the urban expansion of the city of Cape Town, management should focus on the peri-urban habitats.…