Niche divergence and environmental filtering regulate the assembly of a Neotropical larval anuran metacommunity

Background/Question/Methods

Environmental characteristics and the evolutionary history of lineages interact to determine species coexistence in a metacommunity. Traits that determine how species use resources may diverge from or remain similar to ancestors. Concurrently, species select habitats to match their traits with abiotic characteristics and maximize their fitness. Our goal was to test if tadpole co-occurrence pattern in ponds is related to environmental variables, considering the phylogenetic relationships among species. We predict that differences in pond characteristics affect the co-occurrence pattern of tadpoles and that closely related species will co-occur more than expected by chance, assuming a high phylogenetic signal in traits. We sampled tadpoles in 13 ponds in an area of Atlantic Forest from southeastern Brazil, between September 2011 and March 2012. We tested the influence of hydroperiod, pond canopy cover, temperature, and pH on the co-occurrence of tadpoles. We employed a methodology recently proposed, constituted by null model tests and metrics to simultaneously link different patterns of species co-occurrence (checkerboard, clumping, and togetherness) to phylogeny and environmental variables. Checkerboard pattern indicates that two focal species do not co-occur in one site, clumping is a measure of species aggregation across sites, and togetherness indicates species pairs with similar habitat requirements. 

Results/Conclusions

Our results demonstrate how evolutionary and ecological processes influence differently these three patterns at the metacommunity scale. Specifically, we found that (i)clumped species pairs were also closely-related and co-occurred in ponds with similar temperatures; (ii)pH and hydroperiod strongly influenced habitat selection as captured by the togetherness pattern; (iii)closely-related species pairs avoided ponds with contrasting values of temperature and canopy cover; (iv)pond canopy cover influenced the species with checkerboard pattern, i.e., species were segregated between closed- and open-canopy areas. This approach demonstrates how different ecological and evolutionary processes are involved in metacommunity assembly. However, the novelty of this study is that we found that the interplay between these processes depends on the phylogenetic relationship and the co-occurrence pattern.