Microclimatic Fluctuation throughout the Day Influences Subtropical Fruit-Feeding Butterfly Assemblages between the Canopy and Understory

Abstract

Vertical stratification is a recognized pattern in tropical forests; however, biotic and abiotic factors driving this pattern are little explored. We investigated the influence of daily climatic variation in the vertical stratification of fruit-feeding butterfly assemblages sampled with bait traps in the understory and canopy of a subtropical Atlantic Forest. Overall, 1347 individuals belonging to 38 species of fruit-feeding butterflies were recorded. The canopy and understory are distinct concerning diurnal but not nocturnal microclimatic conditions, leading to different responses in community structure. Richness did not differ between strata, but we observed an effect of stratum in interaction with variation in microclimatic conditions, with the canopy increasing in abundance compared to the understory. Temperature homogenization at night can hinder vertical stratification in richness, while microclimatic variation influences species abundance. The species composition was affected by strata with high turnover in the understory, without an effect of microclimatic variables in beta diversity. In addition to the difference in composition, our study shows that the understory was represented mainly by species from Satyrinae, while the canopy presented species from different clades. This could be an artefact of habitat structure, and the species adapted to the closed forest have a dispersal limitation compared to in the canopy. These findings help us to better understand the mechanisms generating distinct patterns of vertical stratification of fruit-feeding butterflies in the Neotropics and provide new insights into the role of microclimatic conditions in the structure of insect assemblages.