Arthropod community composition in urban landscapes is shaped by both environmental filtering and dispersal limitation

We assessed the relative importance of environmental filtering and dispersal limitation in structuring foliage- and ground-dwelling arthropod communities in central North Carolina. We hypothesized that differences in both local environment and dispersal distance between sites would predict differences in community composition, but that dispersal distance would be more important for ground arthropods than for foliage arthropods. We used variance partitioning to quantify the relative explanatory power of differences in the local environment and dispersal distance between sampling plots. For foliage arthropods, the full set of predictors explained 37-39% of the variance in community dissimilarity, while the full set of predictors explained 42-56% of the variance for ground arthropods. Environmental predictors alone consistently explained more variance in community dissimilarity than geographic predictors alone for ground arthropods, but the variance explained by each predictor set alone varied for foliage arthropods depending on the metric of community dissimilarity. Examining communities of multiple arthropod groups across the same spatial gradient highlights the scale-dependence of these processes and illustrates how variation in the environment can alter the relative abundance of specialist and generalist taxa.