Conservation in human-influenced areas : epigaeic arthropods in the Cape Floristic Region Lowlands

[摘要] ENGLISH ABSTRACT: The conservation of biodiversity is becoming increasingly challenging as habitats aredisturbed, fragmented or destroyed. Although nature reserves now cover more than 10 %of the earths' surface it has become clear that more will have to be done to ensure thelong-term survival of species. Therefore, focus is increasingly shifting towardsconserving biodiversity in natural and semi-natural remnants in human-influenced areas.This study aimed to determine the contribution of remnants in human-influenced areas tothe conservation of biodiversity in the Cape Floristic Region (CFR) lowlands, usingground-dwelling arthropods, specifically ants, as the focal taxon. Initially, base-lineinformation of arthropods and in particular ants was obtained. Sampling arthropodsgenerally involves a large sample effort. Therefore maximizing sampling effort for antsin the CFR was investigated by trapping ground-dwelling ants at a single locality.Doubling the number of grids of pitfall traps was found to be more effective in trapping agreater number of species than doubling the duration of sampling. Therefore increasingspatial sampling intensity rather than sampling duration maximizes sample effort for CFRants. Also, the seasonal changes of ground-dwelling arthropods, including ants, weredetermined by sampling four times during the year at a single locality. Overall arthropodabundance was found to peak in summer while dropping to a minimum in winter. Thispattern was mirrored by that of the ants, indicating that ant results have a broaderrelevance than to ants only. The ground-dwelling fauna was dominated by antsemphasizing their importance in the CFR lowlands, and demonstrating that ants are anappropriate flagship taxon for epigaeic arthropod diversity in the CFR. Finally thecontribution of remnants in human-influenced areas to the conservation of the CFR wasinvestigated. A nested hierarchical approach was used, where five localities were selectedacross the CFR, each containing one reserve site and one site with natural remnants. Antswere sampled, along with environmental variables, namely weather, vegetation and soil.Overall, remnants were found to support similar ant assemblages to those of reserves.However for individual localities some remnants were significantly different to theirreserve counterparts. Differences in ant assemblages were found to be greater betweenlocalities than between reserves and remnants. The relatively high heterogeneity of ants found in this study emphasizes the conservation significance of invertebrates along withthat of plants in the CFR. Remnants clearly show the potential to conserve antassemblages, however correct management is needed for these areas to maximize theirpotential. Disturbances such as the presence of the invasive Argentine ant and increasingsoil nutrients by fertilization, pose a distinct threat to the ability of remnants to conserveant assemblages. This study has shown that remnants currently support ant assemblagesrepresentative of those present in the CFR today. Therefore, some remnant patches ofhabitat in agricultural areas currently do contribute highly to the conservation of afunctional important taxon in this global biodiversity hotspot, and if managed correctly,may continue to do so in the future.

[发布机构] Stellenbosch University