Positive co‐occurrence between feeding‐associative savannah fishes depends on species and habitat

Abstract

Abstract Understanding the relative importance of abiotic factors and biotic interactions in determining species co‐occurrence is a fundamental goal in ecology. Most studies of ecology of freshwater fishes have focused on negative biotic interactions (competition and predation), and much less is known about more positive interactions. The goal of this study was to quantify the relative importance of habitat features and biotic interactions (positive and negative) on co‐occurrence of three pairs of feeding‐associative Leporinus (L.) fishes in rivers of central Brazil (L. friderici–L. octomaculatus, L. striatus–L. octomaculatus, L. friderici–L. striatus). We sampled 146 sites on two rivers of central Brazil and used two‐species occupancy models to examine the relative importance of habitat features and commensalistic feeding association for determining co‐occurrence of the three species pairs. Using an information–theoretic framework, we compared weight‐of‐evidence for models containing effects of habitat covariates only, biotic interactions only, and their combination. Model evidence supported the hypothesis that feeding activity of L. friderici facilitates occurrence of L. octomaculatus and that the interaction is mediated by habitat covariates. In contrast, most evidence suggested that occurrence of L. striatus is independent of L. friderici, and is instead determined entirely by habitat features. Evidence for facilitation of L. octomaculatus by L. striatus was mixed—there is evidence supporting the habitat‐only hypothesis as well as habitat‐mediated facilitation. Our results suggest that positive interactions can affect co‐occurrence among freshwater fishes, at least for species that interact strongly. More facultative interactions, such as those between L. friderici and L. striatus, may be less important, at least in certain abiotic contexts. This study indicates that biotic interactions between species of freshwater fish can be evident beyond the microhabitat scale to positively influence species co‐occurrence and adds to evidence from other groups of freshwater organisms indicating the importance of biotic interactions in facilitating species co‐occurrence.