An experimental study of spiders in a shrub-steppe ecosystem: the effects of prey availability and shrub architecture

Abstract

Habitat structure is of great importance for the distribution and abundance of various organisms. Spiders are especially sensitive to structural features of their environment. Although spiders are influenced by habitat structure, it remains unclear whether spiders respond to architecture, to differences in prey availability associated with different architectures, or both. Here, we investigated the effects of shrub architecture and prey availability and their interactions on a spider community in a shrub-steppe environment in northern Utah, USA. Big sagebrush shrubs, matched by size, were randomly assigned to six experimental treatments: two levels of prey attractant (shrubs were either baited or not baited) and three levels of foliage density (low, natural/control, or high). We found that spider abundance and species richness were affected by both prey availability and shrub architecture, while variation in spider species diversity (Shannon-Wiener index) was governed by changes in shrub architecture. Spider species and family compositions were also associated with changes in shrub architecture, although guild composition was not. We discuss the implications and limitations of these findings and present suggestions for future research.