Elevation modulates how Arctic arthropod communities are structured along local environmental gradients

The organization of ecological communities along local environmental gradients provides important information about how such communities may respond to environmental change. In the Arctic, the importance of gradients in shrub cover and soil moisture for non-marine arthropod communities has been clearly demonstrated. By replicating studies along shrub and moisture gradients at multiple elevations and using space-for-time substitution, it is possible to examine how arthropod communities may respond to future environmental change. We collected and identified 4640 adult specimens of spiders and beetles near Narsarsuaq, South Greenland between 8 July and 25 August, 2014 from 112 pitfall traps. The traps were arranged in eight plots covering local gradients in either soil moisture or tall shrub dominance at both low and high elevation. Multivariate generalized linear models revealed that community composition was significantly related to shrub height and soil moisture, and that this relationship varied between low and high elevation. Among the 46 species we found, more species were unique to the high elevation plots than to the low elevation plots, a finding that was most pronounced for spiders in plots along soil moisture gradients. Indicator species analysis corroborated earlier findings of the indicator value of specific species in Greenland and suggested that beetles may serve as better indicators of specific habitats than spiders. The location of plots along local environmental gradients allowed us to detect fine-scale variation in arthropod communities. Together, our results suggest that Arctic arthropod community responses to environmental change may differ among low and high elevation sites.