The influence of species traits and q-metrics on scale-specific β-diversity components of arthropod communities of temperate forests

Protection of biodiversity and ecosystem functions requires a better understanding of spatial diversity. Here we studied diversity patterns of true bugs and saproxylic beetles, sampled in 28 forest stands of southern Germany, using a hierarchical nested design of five increasingly broader spatial levels: trap location, stratum, forest stand, forest site, and ecoregion. We predicted that: (1) for large body-sized species (as a surrogate for highly mobile species) and host generalist species (low host specificity), the proportion of beta-diversity decreases from small to large spatial scales; and (2) the differences between trait-based functional guilds in the proportion of beta-diversity increase with increasing weighting of more-abundant species. Our results indicated that the ecoregion level is the most important diversity scale for both taxa and among functional guilds sampled, followed by the forest stand level. Specialized species were more strongly affected on the ecoregion level than generalist species. Differences in the proportion of beta-diversity between functional guilds increased with increasing weighting of abundant species. The beta-diversity patterns based on body size and host specificity were similar for true bugs, but partly contrasting for saproxylic beetles. Our results suggest that (1) future conservation schemes should focus on establishing new conservation sites in new ecoregions, rather than on enlarging existing protected areas; (2) host specificity might be a more meaningful trait than body size to be considered in biodiversity studies; and (3) common conservation approaches restricted to only large, conspicuous, but rare species might result in a mismatch of important biodiversity scales.