The utility of an index of biotic integrity in predicting terrestrial frog species diversity in a tropical forest

Indices of Biotic Integrity (IBI) summarize multiple metrics of habitat quality. They can be useful tools for rapid ecological assessments to understand the effects of landscape-scale changes on ecological communities. While such indices have already been applied to amphibian communities in wetlands and streams, little is known on their utility for predicting leaf-litter frog communities in tropical forest. Here, we tested how species richness, abundance, and composition of leaf-litter frogs are affected by an IBI in a tropical rainforest in Brazil. We sampled frogs using pitfall traps in 10 sites for five months. We used Generalized Linear Models to model species abundance and richness, and a model-based method called Generalized Linear Latent Variable Model to model species composition while considering the interaction between body size and IBI. Additionally, we provide novel occurrence and life-history data for species in an adjacent area sampled using multiple survey methods. We found 14 species in pitfall traps and 34 overall. Neither species richness, abundance, nor composition were affected by the IBI, with models explaining as little as 7% of variation in the data. However, the response of species to it depended on their body size, with the abundance of Ischnocnema henselii being positively, while that of Physalaemus olfersii and Adenomera marmorata being negatively influenced by IBI. Overall, the abundance of large-bodied species was positively, although weakly, associated with IBI. The high biotic integrity, along with the small extent of the study area can be possible explanations for these results. Our findings provide a new perspective to the utility of using indices of biotic integrity to assess the response of terrestrial vertebrates to habitat change.