Body size, colony size, abundance, and ecological impact of exotic ants in Florida's upland ecosystems

摘要

Questions: Do naturalized exotic ant species have larger colonies and smaller workers relative to co-occurring native species? Do exotic ant species have a negative impact on the co-occurring ant and arthropod fauna in undisturbed native upland ecosystems? Study system: Native and exotic ants sampled from four kinds of native upland ecosystems and one kind of disturbed ecosystem (fields) in north-central Florida. This fauna included a total of 94 species, 13 of which are exotic, from five different ecosystems. Methods: Ants were intensively surveyed using a transect-based sampling design and four sampling methods (pitfalls, litter samples, baits, and hand collecting). We estimated average worker body weight and average colony size for all of the species, together with the relative abundance and species richness of native, exotic, and endemic species within ecosystems. Results: The average body size of exotic ants was not obviously different from that of native species. The average colony size of exotic ants was smaller than that of native species, with the exception of Solenopsis invicta, which had the largest colony size of all species. Introduced ants (including S. invicta) were neither speciose nor abundant in any of the native woodland ecosystems. In contrast, in disturbed sites exotic ants accounted for about 40% of total ant abundance and 25% of species richness. Florida's intact, native upland ecosystems appear to be resistant to invasion of exotic ant species despite the fact that surrounding disturbed habitats host a large diversity and abundance of introduced species.