Beetle trophic groups show differential effects of phylogeny and environment along a successional gradient

The interplay between evolutionary history and environmental filtering is crucial in understanding the forces that determine community assembly. In particular, whether community assembly is structured by phylogenetic factors or by functional traits of species remains very controversial. This study uses a combination of functional trait and community phylogenetic approaches to disentangle successional and phylogenetic filtering effects on functional characteristics of beetle detritivore and predator metacommunities across a post-logging forest succession gradient. We found significant environmental filtering on traits with only limited evidence of trait dispersion for both detritivores and predators, possibly suggesting that biotic interactions are not as important for beetle community assembly. However, phylogenetic signal and structure differed dramatically between the groups, with predator traits being more phylogenetically constrained at the species and community level compared to detritivores. However, predators showed little variation in phylogenetic structure across successional stages, whereas community changes in detritivores were strongly linked to phylogeny. Between trophic groups, traits responded differently to forest succession enabling us to characterise different functional syndromes for predators and detritivores. More generally, when phylogenetic autocorrelation was controlled, detritivore communities had significant individual trait-environment relationships whereas predator species were more constrained by environment alone. Our study provides novel insights into community assembly patterns for beetles across forest succession, but furthermore it demonstrates the exciting potential of this combined approach to make worldwide comparisons of arthropod communities.