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Gigliotti LC, Berg ND, Boonstra R, Cleveland SM, Diefenbach DR, Gese EM, Ivan JS, Kielland K, Krebs CJ, Kumar AV, Mills LS, Pauli JN, Underwood HB, Wilson EC, Sheriff MJ. Latitudinal variation in snowshoe hare (Lepus americanus) body mass: a test of Bergmann’s rule. CAN J ZOOL 2020. [DOI: 10.1139/cjz-2019-0184] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The relationship between body size and latitude has been the focus of dozens of studies across many species. However, results of testing Bergmann’s rule — that organisms in colder climates or at higher latitudes possess larger body sizes — have been inconsistent across studies. We investigated whether snowshoe hares (Lepus americanus Erxleben, 1777) follow Bergmann’s rule by investigating differences in body mass using data from six published studies and from data of 755 individual hares captured from 10 populations across North America covering 26° of north latitude. We also explored alternative hypotheses related to variation in hare body mass, including winter severity, length of growing season, elevation, and snow depth. We found body mass of hares varied throughout their range, but the drivers of body mass differed based on geographic location. In northern populations, females followed Bergmann’s rule, whereas males did not. In northern populations, male mass was related to mean snow depth. In contrast, in southern populations, body mass of both sexes was related to length of the growing season. These differences likely represent variation in the drivers of selection. Specifically, in the north, a large body size is beneficial to conserve heat because of low winter temperatures, whereas in the south, it is likely due to increased food supply associated with longer growing seasons.
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Affiliation(s)
- Laura C. Gigliotti
- Department of Forestry and Environmental Conservation, Clemson University, 261 Lehotsky Hall, Clemson, SC 29634, USA
| | - Nathan D. Berg
- U.S. Fish and Wildlife Service, National Wildlife Refuge System, Anchorage, AK 99503, USA
| | - Rudy Boonstra
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada
| | - Shawn M. Cleveland
- Department of Environmental and Forest Biology, State University of New York College of Environmental Science and Forestry, Syracuse, NY 13210, USA
| | - Duane R. Diefenbach
- U.S. Geological Survey, Pennsylvania Cooperative Fish and Wildlife Research Unit, Pennsylvania State University, University Park, PA 16802, USA
| | - Eric M. Gese
- U.S. Department of Agriculture, Wildlife Services, National Wildlife Research Center, Department of Wildland Resources, Utah State University, Logan, UT 84322, USA
| | - Jacob S. Ivan
- Colorado Parks and Wildlife, Fort Collins, CO 80526, USA
| | - Knut Kielland
- Department of Biology and Wildlife, Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - Charles J. Krebs
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Alexander V. Kumar
- Wildlife Biology Program, University of Montana, Missoula, MT 59812, USA
| | - L. Scott Mills
- Wildlife Biology Program, University of Montana, Missoula, MT 59812, USA
- Office of the Vice President for Research and Creative Scholarship, University of Montana, Missoula, MT 59812, USA
| | - Jonathan N. Pauli
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - H. Brian Underwood
- U.S. Geological Survey, Patuxent Wildlife Research Center, Tunison Laboratory of Aquatic Science, Cortland, NY 13043, USA
| | - Evan C. Wilson
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Michael J. Sheriff
- Biology Department, University of Massachusetts Dartmouth, Dartmouth, MA 02747, USA
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