Diversity of anuran communities facing bullfrog invasion in Atlantic Forest ponds

Abstract

Invasive species may affect community diversity in several ways, causing species loss at local scales and promoting either biotic homogenization among sites within a region or increases in beta diversity among regions. If these losses or additions are restricted to specific functional groups or clades, it could mean the loss or modification of an ecosystem process, and cause important changes in native community structures. In this study, we assessed whether a bullfrog invasion is related to diversity changes in Atlantic Forest anuran communities. We compared communities from invaded and non-invaded sites, and tested for differences in composition and in the variability of composition, at both taxonomic and phylogenetic levels. The potential influence of pond and habitat features in our results was also assessed. We also tested if bullfrog invasion is promoting nestedness. We found no differences among anuran compositions from 57 invaded and non-invaded sites, across the three regions studied, either for taxonomic or for phylogenetic data. Habitat descriptors partially explained taxonomic composition. The taxonomic and phylogenetic compositions were also similar regarding dispersion variability. In addition, invaded sites did not show nested compositions from non-invaded sites. In sum, our results do not support the hypothesis that bullfrog invasion caused changes in diversity patterns of anuran communities. Our results contrast with studies conducted in other regions of the world, where invasive populations of bullfrogs seem to affect local native communities. In those places, bullfrogs find congeneric or confamilial species, which may be more affected by the invasion. In the Atlantic Forest, bullfrogs find suitable climatic conditions, and may face low biotic resistance since they find no congeneric species. These conditions may allow bullfrogs to coexist with native species without changes in diversity.