Spider Community Organization: Seasonal Variation and the Role of Vegetation Architecture

Abstract

The relationships between vegetation architecture and spider community attributes were examined in a big sage ( Artemisia tridentata ) community. Spiders were separated into guilds using similarities of species' hunting behavior. Shrub architecture was experimentally manipulated in the field by either clipping 50% of a shrub's foliage to decrease foliage density or tying together a shrub's branches to increase foliage density. Shrub perturbations resulted in changes in the number of spider species, spider guilds and guild importance values. The number on spider species and guilds in the tied shrubs were significantly higher than those in the clipped or control shrubs sampled. Spider species diversity and the number of species and guilds were positively correlated with indicators of shrub volume and shrub foliage diversity. This suggests that structurally more complex tied shrubs can support a higher number of spider Species and species diversity. Temporal patterns of the number of spider species, and species diversity (H') showed midsummer peaks m both 1974 and 1975. Evenness (J') remained relatively constant through both seasons. The data suggest that architectural properties of habitat may be an important determinant of the distribution and species diversity of predatory invertebrates.