Recovery of invertebrate diversity in a rehabilitated city landscape mosaic in the heart of a biodiversity hotspot

We investigate here invertebrate response to alien pine plantations, their removal in comparison with natural vegetation, recovering indigenous forests and a botanical garden around Cape Town, South Africa, within a biodiversity hotspot. Pines had low invertebrate species richness and abundance. The botanical garden had the highest species richness and abundance. Natural fynbos vegetation was more similar to pines than to recovering fynbos, while recovering forest was more similar to pines than to any other site. The botanical garden is a major refugium for invertebrate species. Surprisingly, invertebrate assemblages in natural fynbos were more similar to those in pines than in recovering fynbos after the removal of pines. This suggests that some invertebrate species colonize the fynbos soon after rehabilitation disturbance, a response similar to the influence of fire. However, it takes longer for other natural climax invertebrate species to establish, some of which find refuge in pines and the botanical garden. Invertebrate assemblages of indigenous natural forests are more difficult to restore than those of fynbos, thus the protection of the remaining natural forests is a conservation priority. Invasive alien Argentine ant (Linepithema humile) was far more abundant in recovering fynbos than in natural fynbos or in the botanical garden and pines. It benefits from initial restoration disturbance, although is likely to decline as the natural fynbos mature. This study strongly supports removal of alien pines in an urban context, and also emphasizes that an urban botanical garden of indigenous plants has major invertebrate conservation value.