The Role of Fine-Scale Habitat Associations in Structuring Spider Assemblages: Determinants of Spatial Patterns in Community Composition

Abstract

Ecologists strive to identify the mechanisms that drive the identity and abundance of species in different locations, because a better understanding of such factors enables them to better predict the effects of habitat modification on organisms, and to identify landscapes in which species are likely to benefit from conservation interventions. However, there is still no consensus on the mechanisms behind geographical variation in species diversity. The primary objective of this dissertation was to focus on spider assemblages to investigate how the fine-scale habitat associations of organisms may drive the composition of their communities at larger scales. Research was conducted in the Bear River Mountains, Utah, in an attempt to elucidate the potential role of species-microhabitat associations in driving three well-known patterns of community composition that have been typically investigated at broad scales: 1) elevation gradients of species diversity, 2) the response of species assemblages to neighboring habitat structure and 3) community composition at the edges of habitat patches. I found that fine-scale topographic variables related to slope aspect may play an important role in shaping elevational patterns of species composition. In addition, two species characteristics that may be useful predictors of sensitivity to habitat modification at larger scales were identified: mobility and habitat preference. This work suggests that a better understanding of the links between the biological traits of species and their fine-scale environmental requirements may help uncover the mechanisms between spatial patterns of community composition at larger scales