Variation in beetle community structure across five microhabitats in Australian tropical rainforest trees

Abstract

Abstract Beetles (Coleoptera) are the most species‐rich and ecologically diverse group of organisms in tropical rainforest canopies. This study reports on the distribution of the beetle community on five discrete canopy microhabitats (mature leaves, new leaves, flowers, fruit, and suspended dead wood) on 23 tree species in an Australian tropical rainforest. We tested the hypothesis that the beetle fauna will vary in community structure between microhabitats based on differences in the quantity, quality as a food source and availability of different canopy microhabitats. There was substantial variation in dominant beetle families in terms of abundance between microhabitats. All assemblages contained a high number of rare species, with flowers supporting most of the more abundant species. Consequently, the flower‐visitor assemblage was more heterogeneous than expected by chance, whereas the mature leaf assemblage was more even in the proportional abundances of species than expected. The distribution of singletons was also non‐random and flowers, which are spatially and temporally restricted, supported fewer singletons than expected by chance, whereas mature leaves and dead wood supported more. These differences were insensitive to beetle feeding guild, and are most likely related to variation in microhabitat distribution and availability, which influenced relative sampling efforts and the probability of random microhabitat/beetle associations. High dissimilarity in species overlap between microhabitats suggests that each microhabitat attracts a unique beetle assemblage, which has an additive effect on canopy‐wide species richness patterns. Consequently, biodiversity studies that focus on single microhabitats may inadvertently omit a large proportion of canopy species.