The importance of habitat structure in conservation studies is widely recognized, as is the potential value of arthropods in conservation assessments. Various arthropods, including spiders, are well suited for ecological studies because of their taxonomic diversity and ubiquity. Although spiders are widely known to be influenced by habitat structure and are emerging as organisms of interest in habitat assessment, it remains unclear whether spiders are responding to architecture or to differences in prey availability associated with different architectures. The purpose of this study was to investigate the effects of habitat structure and insect availability and their interactions on spider abundance and diversity. Big sagebrush shrubs (Artemisia tridentata) were randomly assigned to six experimental treatments. Treatments consisted of two levels of insect attractant (shrubs that were either baited or not baited) and three levels of foliage density (low, natural/control, or high foliage density shrubs). A double repeated measures ANOVA was used to evaluate the significance of differences among treatments.
Results/Conclusions
A total of 7,331 spiders representing at least 30 species were collected during 2007 and 2008. Members from the family Salticidae were numerically dominant, followed by Philodromidae, Oxyopidae, Dictynidae, and Theridiidae. Other families include Araneidae, Gnaphosidae, Linyphiidae, Lycosidae, Mimetidae, and Thomisidae. Spiders (and insects) were more numerous on baited, natural and high foliage density shrubs. Spider diversity (as measured by Shannon and Simpson indices) was highest on natural and high foliage density shrubs. The effect of insect availability on spider diversity was only significant with respect to the interaction between year and insect availability. In 2007, spider diversity was highest on baited shrubs. Spider species richness, abundance, and diversity were seasonal with higher values being reported in June. Insect abundance was also highest in June.
