The influence of scale and patchiness on spider diversity in a semi-arid environment

Semi-arid scrubland in the Middle East consists of a soil crust matrix overlain with patches of perennial shrubs. To understand factors influencing biodiversity in this vulnerable landscape we need to understand how this mosaic of habitats influences associated fauna. Spiders are particularly abundant in this habitat so we asked if spider diversity differed between habitat patches and if different patch types contained either a subset of the regional species pool or specific species guilds. We also asked whether changes in the fractal nature of the microphytic and macrophytic patch mosaic altered spider diversity in this habitat. We found that the semi-arid scrubland at Sayeret Shaked Park (Israel) contains different spider communities that require patches of a certain quality to develop fully. Different patch types contain communities of different species, but the community structure of the patches is similar. We suggest that large-scale environmental factors typical of the site as a whole influence coarse-grained community structure, while small-scale differences between patch types result in the specialisation of species to different patch types.