Broad-scale gradients of resource utilization by phyllostomid bats in Atlantic Forest: patterns of dietary overlap, turnover and the efficacy of ecomorphological approaches.

Abstract

Identifying mechanisms that promote coexistence at the local level is enigmatic for many organisms. Numerous studies have indirectly demonstrated that biotic interactions may not cause deterministic patterns reflective of the coexistence of interacting bat species. Nonetheless, demonstration of the partitioning of resources by phyllostomid bats by directly examining diet matrices may illuminate a mechanism of coexistence. I examined the dietary overlap of phyllostomid bats across 23 sites in the Atlantic Forest of South America. I also examined components of beta diversity (turnover and nestedness) of resources among species as well as the degree to which morphology can act as a surrogate for dietary similarity in each community. Bats exhibited high overlap. Nonetheless, dietary beta diversity was more related to turnover than nestedness of items suggesting substantive species-specific affinities. Niche breath and dietary overlap were positively related tothe number of species and the number of resources consumed in communities. Accordingly, changes in richness across Atlantic Forest may be facilitated by increases in resources available at the community level. There were positive, yet weak relationships between morphological and dietary distance. The relationship between morphology and diet was invariant relative to geography, species richness, number of dietary resources, average diet breadth and average dietary overlap indicating that in the Atlantic Forest morphology is a consistent surrogate of dietary relationships of species. Atlantic Forest is one of the most anthropogenically modified tropical forests in the world. This in combination with distinct climatic seasonality likely causes higher dietary overlap, weaker ecomorphological relationships and persistence of only the most general bat species.