Rapid morphological divergence in two closely related and co-occurring species over the last 50 years
We studied morphological variation in two closely related and ecologically similar species of mice of the genus Peromyscus, the deer mouse (P. maniculatus) and white-footed mouse (P. leucopus), over the last 50 years in Southern Quebec. We found that contemporary populations of the two species are distinct in morphology and interpret this differentiation as a reflection of resource partitioning, a mechanism favouring their local coexistence. While there was no size trend, geographic or temporal, both species displayed a concomitant change in the shape of their skull over the last 50 years, although this change was much more apparent in the white-footed mouse. As a result, the two species diverged over time and became more distinct in their morphology. The observed changes in morphology are large given the short time scale. During this period, there was also a shift in abundance of the two species in Southern Quebec, consistent with the northern displacement of the range of the white-footed mouse in the last 15 years. Our study thus reports the changes in morphology of two co-occurring mammal species that were accompanied by changes in distribution and local abundance, potentially in response to rapid climate change.
KeywordsCharacter displacement Morphometry Peromyscus Rodent Phenotypic variation Species segregation
We are grateful to landowners and park managers, the staff at the Gault Nature Reserve, field-work assistants and the many graduate students who participated in specimen collection, A. Howell for his help with the Redpath Museum specimens, K. Khidas at the Canadian Museum of Nature, R. Smith who collected the data used in Fig. S2, A. Cardini, the editor and associate editor, and two anonymous reviewers for comments on a previous draft of this manuscript. This work was supported by a FQRNT Team Grant #147236 to VM and AG, NSERC Discovery Grants # 341918-2012 to VM and # 2014-05840 to AG, a Canada Research Chair Tier 1, a Liber Ero Chair and Killam Fellowship to AG, and support from the LabEx Sciences archéologiques de Bordeaux (#ANR-10-LABX-52) to RL.
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