Identifying the scale of effect of habitat for diversity and biomass of multiple arthropod taxa

Abstract

Abstract Context Understanding how landscape composition influences biodiversity is a central objective of landscape ecology. Because species respond to environmental conditions across different spatial scales, landscape effects are inherently scale-dependent, making the identification of ecologically relevant spatial scales essential for robust analyses of patterns in insect communities. Objectives We investigated the spatial scale at which landscape variables across habitats best explain insect biomass and diversity of (I) whole insect communities, (II) different taxonomic and functional groups and (III) tested whether empirically identified optimum scales of effect support common assumptions regarding the mobility and the trophic level of taxonomic groups. Methods We quantified insect communities in gradients of land-use intensity and climate using data from 1293 Malaise trap samples from 179 plots in southern Germany to analyze the variance explained by environmental factors at different radii around sampling sites. We estimate the respective scale of effect for total insect biomass and diversity, as well as for different taxa and functional groups, using sample coverage standardized measures for diversity and a novel approach to estimate biomass for subgroups via sequencing reads. Results We find that the scale of effect of landscape variables differed between insect biomass and diversity. Overall diversity, as well as the diversity of most subgroups, was best explained by local habitat conditions (100—500 m). In contrast, although local conditions also contributed to explaining variation in overall biomass, larger scales (1500—2000 m) provided the strongest explanatory power. However, patterns differed between rare and dominant species. In addition, we could not confirm common assumptions with respect to species mobility or trophic level. Conclusions Our findings highlight the importance of a thorough selection of the landscape scale when assessing diversity and biomass variables or taxon-specific groups and provide suggestions for the most suitable scale to be selected depending on the target variable under study in insect community research.