Скачать или смотреть Elmer C Birney Award Presentation - Rachel Walsh

Understanding range shifts by chipmunks in Yosemite: importance of interspecific spatial overlap and habitat use
Rachel E. Walsh* and Eileen A. Lacey

Despite substantial evidence that global climates are changing, predicting organismal responses remains challenging, as responses can vary dramatically, even among closely related species. To explore ecological reasons for this variation, we compared patterns of spatial overlap and habitat use in two chipmunk species (genus Tamias) that have shown markedly different patterns of elevational range change over the past century: the alpine chipmunk (T. alpinus) experienced a significant elevational range contraction, while the elevational range of the partially sympatric lodgepole chipmunk (T. speciosus) did not change appreciably. To quantify interspecific spatial overlap and contrast patterns of habitat use, we combined live-trapping and radio-tracking of chipmunks with analyses of vegetation cover (Normalized Difference Vegetation Index). We found considerable spatial overlap between these species, indicating that interspecific competition may play a role in mediating range responses in these animals. In areas of sympatry, habitat use differed between the study species, with T. alpinus typically found in habitats with lower NDVI values than those associated with T. speciosus. The range of habitats used by T. alpinus was also less than that used by T. speciosus. These results are consistent with emerging evidence that greater ecological specialization by T. alpinus may be associated with stronger response to environmental change. Our work underscores the importance of integrating information on multiple biotic factors when attempting to explain responses to climate change. This work was supported by an ASM Grant-in-Aid of Research awarded to Rachel E. Walsh in 2012.