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Spatial segregation of sympatric marten and fishers: the influence of landscapes and species-scapes

Authors


J. T. Fisher, Alberta Innovates – Technology Futures, Ecosystem Management Unit. no. 3-4476 Markham St., Victoria, BC V8Z 7X8, Canada. E-mail: jason.fisher@albertainnovates.ca

Abstract

Co-occurring species are rarely considered as a factor influencing habitat selection. However, niche theory predicts that sharing resources, predators, and other interspecific interactions can limit the environmental conditions under which a species may exist. How does the spatial distribution of one species affect that of another within shared landscapes? We tested whether sympatric marten Martes americana and fishers M. pennanti in a mountain landscape in Alberta, Canada exhibit local-scale spatial segregation, beyond differential habitat selection. We modelled marten and fisher distribution in relation to remotely-sensed habitat data and species co-occurrence, using generalized linear models and information-theoretic model selection. Marten and fishers selected different habitat types and showed different responses to habitat fragmentation. Even after accounting for these differences, the absence of one species significantly explained the occurrence of the other. We conclude that the spatial distribution of marten and fishers influences habitat selection by each other at landscape scales, and hypothesize that this pattern may result from competition in a spatially heterogeneous environment. Species-habitat models that consider only resources may fail to capture key predictors of species’ occurrence. Reliable prediction and inference requires that ecologists expand from landscapes to also include species-scapes: a spatial plane of species interactions that combines with resources to drive species’ distributions.

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