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Small mammal diversity loss in response to late-Pleistocene climatic change


Communities have been shaped in numerous ways by past climatic change; this process continues today1. At the end of the Pleistocene epoch about 11,700 years ago, North American communities were substantially altered by the interplay of two events. The climate shifted from the cold, arid Last Glacial Maximum to the warm, mesic Holocene interglacial, causing many mammal species to shift their geographic distributions substantially2,3. Populations were further stressed as humans arrived on the continent4. The resulting megafaunal extinction event, in which 70 of the roughly 220 largest mammals in North America (32%) became extinct5, has received much attention. However, responses of small mammals to events at the end of the Pleistocene have been much less studied, despite the sensitivity of these animals to current and future environmental change. Here we examine community changes in small mammals in northern California during the last ‘natural’ global warming event at the Pleistocene–Holocene transition and show that even though no small mammals in the local community became extinct, species losses and gains, combined with changes in abundance, caused declines in both the evenness and richness of communities. Modern mammalian communities are thus depauperate not only as a result of megafaunal extinctions at the end of the Pleistocene but also because of diversity loss among small mammals. Our results suggest that across future landscapes there will be some unanticipated effects of global change on diversity: restructuring of small mammal communities, significant loss of richness, and perhaps the rising dominance of native ‘weedy’ species.

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Figure 1: Location map.
Figure 2: Diversity through time based on standardized abundance data from 1,000 subsamples at n = 132.

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Accession codes

Data deposits

Fossil specimens are deposited in the University of California Museum of Paleontology as localities V99822 and V99785. Modern specimens are deposited in the University of California Museum of Vertebrate Zoology under accession number 14590.


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We thank numerous field assistants, A. Barnosky, C. Li, and members of the J. Williams and E. Hadly laboratories for comments that improved the manuscript. The National Science Foundation (grants EAR-0545648 and EAR-0719429 to E.A.H.), California Energy Commission’s Public Interest Energy Research Environmental Area grant to J.L.B., and the Stanford University Vice Provost for Undergraduate Education supported this research. We are grateful for support from the US Forest Service.

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Authors and Affiliations



J.L.B. planned the project, excavated the deposit, identified specimens, analysed the data and wrote the paper. J.L.M. identified Microtus spp., performed radiocarbon dating and wrote the paper. E.A.H. planned the project, helped excavate the deposit and wrote the paper.

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Correspondence to Jessica L. Blois.

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The authors declare no competing financial interests.

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Blois, J., McGuire, J. & Hadly, E. Small mammal diversity loss in response to late-Pleistocene climatic change. Nature 465, 771–774 (2010).

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