The role of precipitation and host assemblage composition in shaping bat–bat fly network structure

Abstract

Climatic seasonality plays an important role in shaping ecological interactions, including those between bats and their ectoparasitic bat flies. Although previous studies have acknowledged the influence of climate on the structure of bat–bat fly interaction networks, the existence of biogeographical patterns driven by climatic seasonality remains largely unexplored. Because biogeographic patterns reflect recurrent structural changes along environmental gradients, identifying them can provide valuable insights into host–parasite interactions and their responses to environmental variation. Here, we investigated the effects of climatic seasonality on the structure of bat–bat fly interaction networks across the Neotropics, while accounting for host assemblage composition and bat functional traits. We analyzed interaction networks previously compiled from a published paper on bat–bat fly interactions throughout the Neotropics. We obtained climatic variables from WorldClim models, and bat functional traits from published databases. We quantified network structure using network size, niche overlap, modularity, and nestedness. To assess the influence of climate and host traits on network structure, we fitted generalized linear models including mean annual temperature, temperature seasonality, annual precipitation, and precipitation seasonality as explanatory variables. Network size was also included as a predictor to account for its influence on niche overlap, modularity, and nestedness. In addition, we incorporated the proportion of cavity-roosting bats, frugivorous bats, and phyllostomid bats as controls for functional and taxonomic composition of host assemblages. Our results show that higher annual precipitation is associated with larger network size and reduced niche overlap, whereas increasing network size leads to lower nestedness. The proportion of phyllostomid bats further increased niche overlap and reduced nestedness, highlighting the importance of host assemblage composition. In contrast, neither temperature seasonality nor precipitation seasonality had a direct effect on network structure. Overall, our findings emphasize the dominant role of annual precipitation and host assemblage, rather than climatic seasonality, in shaping bat–bat fly interaction networks. These results advance our understanding of parasitism dynamics and the structural organization of antagonistic host–parasite networks at broad biogeographical scales.