Physiological tolerances of three sympatric riparian wolf spiders (Araneae: Lycosidae) correspond with microhabitat distributions

Coexisting species from the same ecological guild often exhibit different adaptations to discontinuous, abiotic environmental factors. In the laboratory, we compared tolerance to thermal and desiccation stress among three sympatric wolf spiders (Pirata sedentarius Montgomery, 1904, Pardosa lapidicina Emerton, 1885, and Pardosa fuscula Thorell, 1875). In the field, we examined spatial structure across a microhabitat (moisture) gradient in a streamside cobble habitat where these three species are abundant. Female R sedentarius succumbed more quickly to desiccation stress than females of either Pardosa species. In the absence of thermal stress, desiccation tolerance was high for both Pardosa species. However, P. fuscula appears to be more resistant to combined thermal and desiccation stress than P. lapidicina. These findings correspond with the results of the field survey; the distribution of P sedentarius was the most restricted (by proximity to the shoreline) among the three species. Contingency analyses also revealed greater relative abundance of P. fuscula than P. lapidicina farther away from the creek. Further examination of spatial structure suggests that neither of these two species was restricted by proximity to the shoreline within the sampling grid.