Effect of environmental gradients on community structuring of aerial insectivorous bats in a continuous forest in Central Amazon

Biotic and abiotic environmental factors influence the abundance and spatial distribution of species and the structuring of communities along environmental gradients. Topography, vegetation structure and food availability have been identified as factors that directly and indirectly influence habitat selection by species in tropical forests. Although the factors that determine community structure in phyllostomid bats have received substantial attention, aerial insectivorous bats have been largely neglected, and their responses to environmental gradients in continuous tropical forests remain poorly understood. In this study, we evaluated how aerial insectivorous bats respond to different environmental gradients in 25 km 2 of continuous preserved forest in Central Amazonia. Our hypothesis was that topography, vegetation structure and food availability influence aerial insectivorous bats. Insect biomass was shown to be the predictor variable with the greatest contribution to the bat species richness, abundance and assemblage composition. Bat activity and richness were positively related to insect biomass. Bat assemblage species composition was also related to terrain elevation and insect assemblage composition. Vegetation clutter did not influence the number of species, abundance and bat assemblage species composition. In contrast, vegetation clutter and terrain elevation influenced some bat species, indicating that the response to these variables was species-specific within the bat assemblage. Our study showed that the food availability, both the quantity and its distribution in the environment, was the main structuring factor of the bat community that occupy higher trophic levels, such as aerial insectivorous bats, in a continuous forest in Central Amazon.