Habitat-specific effects of climate change on a low-mobility Arctic spider species.

Terrestrial ecosystems are heterogeneous habitat mosaics of varying vegetation types that are differentially affected by climate change. Arctic plant communities, for example, are changing faster in moist habitats than in dry habitats and abiotic changes like snowmelt vary locally among habitats. Such differences between habitats may influence the effects of climate changes on animals and this could be especially true in low-mobility species. Suitable model systems to test this idea, however, are rare. We examined how proxies of reproductive success (body size, juvenile/female ratios) and sex ratios have changed in low-mobility crab spiders collected systematically over a 17-year period (1996-2012) from two distinct habitats (mesic and arid dwarf shrub heath) at Zackenberg in northeast Greenland. We identified all adults in the collection to confirm that they represented just one species ( Xysticus deichmanni Sørensen) based on morphology. This provided a unique opportunity to measure recruitment potential because we could assume that all juvenile crab spiders belonged to that species. We determined sex, stage, and size of all specimens ( n = 2,115). Body size variation was significantly related to the timing of snowmelt and differed significantly between the sexes and habitats with the spiders in the mesic habitat showing a stronger temporal response to later snowmelt. Juvenile/female ratios also differed significantly between habitats; as did the overall abundance of individuals. We found significant main effects of snowmelt and habitat on sex ratio with the proportion of females decreasing significantly in response to later snowmelt only in the mesic sites. Effects of climate change may be masked by habitat differences and have implications for future range changes of species at both small and large spatial extents. We recommend that local habitat differences are included in analyses of species responses to climate change. [ABSTRACT FROM AUTHOR]

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