Functional and phylogenetic beta diversity response of nocturnal moth assemblages to land‐use intensity in grasslands and forests

Land‐use intensification is filtering for species, able to cope with anthropogenic landscapes. This was assumed to result in functionally and phylogenetically homogenous communities, but a recent meta‐analysis could not confirm a consistent homogenization response to human pressure and raises open questions. In central Europe, the two major steps of land‐use intensification were the conversion of forests to agriculture, and the intensification of land use within both habitats. Using light trap data of nocturnal moths, we tested the hypothesis of trait filtering and increasing community homogenization, measured by beta diversity, as response to increasing land‐use intensity. The study was conducted in three regions of Germany, each representing well selected and replicated land‐use gradients in forests and grasslands. With increasing land use, we predicted (P1) decreasing functional and phylogenetic beta diversity, (P2) decreasing body size, (P3) increasing wing load and (P4) darker species in communities. We calculated sample coverage standardized functional (FBD) and phylogenetic (PBD) beta diversity along Hill numbers. We found decreasing FBD and PBD with increasing land use within both habitats, but only for common and dominant species, while rare species in forests showed the opposite pattern. In contrast, grasslands, with higher human pressure, showed overall higher PBD compared to forests, while FDB for common and dominant species showed the opposite pattern. Focusing on functional traits, community weighted means showed a decrease in average body size and an increase in wing load and colour darkness with increasing land‐use intensity. These findings corroborate the increasing evidence of a more complex pattern of land‐use effects on beta diversity in species communities, varying in response over relative abundance and focused facets of biodiversity. It also shows how phylogeny can act as a surrogate for functional diversity because closely related species often share similar traits due to their common evolutionary history.