Spatial and Temporal Patterns in a Sagebrush Steppe Spider Community (Arachnida, Araneae)

A total of 83 species of spiders were collected from the shrub, herb and ground strata of a sagebrush steppe in northern Utah. Dominant families (Thomisidae, Philodromidae, Salticidae) and, in some cases, genera (Misumenops, Philodromus) or species [Sassacus papenhoei (Peckham and Peckham)] were similar to those found in other studies of shrub-dominated areas. Among the spiders of this community, ambushing and wandering were more common foraging strategies than was webspinning. Habitat separation in sagebrush steppe spiders was more vertical than horizontal. Shrub and herb spider species assemblage differed sharply from the ground spider species assemblage, less so from one another. Differences in vegetation density, diversity and size among four study plots correlated positively with spider abundance and diversity, but resulted in less difference among spider assemblages. Temporal patterns of spider abundance differed among strata. Seasonal patterns showed evidence of being influenced by climate and migration of spiders between strata. Diel activity patterns were examined only for spiders of shrub and herb strata. Spider activity in the herb stratum was strongly influenced by light intensity, temperature and relative humidity. This was not as clear in shrubs.