Dispersal ability, trophic position and body size mediate species turnover processes: Insights from a multi‐taxa and multi‐scale approach

Aim: Despite increasing interest in β-diversity, that is the spatial and temporal turno-ver of species, the mechanisms underlying species turnover at different spatial scales are not fully understood, although they likely differ among different functional groups. We investigated the relative importance of dispersal limitations and the en-vironmental filtering caused by vegetation for local, multi-taxa forest communities differing in their dispersal ability, trophic position and body size.Location: Temperate forests in five regions across Germany.Methods: In the inter-region analysis, the independent and shared effects of the re-gional spatial structure (regional species pool), landscape spatial structure (dispersal limitation) and environmental factors on species turnover were quantified with a 1-ha grain across 11 functional groups in up to 495 plots by variation partitioning. In the intra-region analysis, the relative importance of three environmental factors related to vegetation (herb and tree layer composition and forest physiognomy) and spatial structure for species turnover was determined.Results: In the inter-region analysis, over half of the explained variation in community composition (23% of the total explained 35%) was explained by the shared effects of several factors, indicative of spatially structured environmental filtering. Among the independent effects, environmental factors were the strongest on average over 11 groups, but the importance of landscape spatial structure increased for less disper-sive functional groups. In the intra-region analysis, the independent effect of plant species composition had a stronger influence on species turnover than forest physi-ognomy, but the relative importance of the latter increased with increasing trophic position and body size.Main conclusions: Our study revealed that the mechanisms structuring assemblage composition are associated with the traits of functional groups. Hence, conserva-tion frameworks targeting biodiversity of multiple groups should cover both envi-ronmental and biogeographical gradients. Within regions, forest management can enhance β-diversity particularly by diversifying tree species composition and forest physiognomy.