The role of climate in limiting the biogeographic ranges of small mammals [Rôle du climat dans la limitation des aires biogéographiques chez les petits rongeurs].

Résumé

In order to provide information about how small mammals might be expected to respond to global climate change, we examined the correlation of several climatic parameters, soil type, and vegetational assemblages with the geographic range boundaries of two adjacent but largely allopatric species of ground squirrels, Spermophilus richardsoni and S. columbianus. Using GIS techniques in ARC/INFO, species ranges were overlain on maps of potentially correlated abiotic factors constructed from the VEMAP database. Apparent correlations were tested for significance by CART analysis and spatial autocorrelation statistics. Results indicate that Spermophilus columbianus may be limited to areas of high snow cover, which provides insulation to keep hibernacula relatively warm. However, S. richardsoni may be kept out of S. columbianus's range by a competitive interaction that focuses on ability to dig effieciently in rocky soils. These results indicate that while climatic parameters may be the main limiter in some cases or in some parts of a given species range, adjacent species may be limited by competitive interactions that have little direct linkage to climatic parameters. Hence, predictions about how mammal communities might respond to ongoing global warming may well be possible because in some cases linkages between species ranges and climatic parameters can be established. However, accuracy in such predictions only will result from analyzing several species within the community to determine the complex interplay between climatic and nonclimatic influences on biogeography.