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16 February 2016 Phylogeographic and population genetic structure of bighorn sheep (Ovis canadensis) in North American deserts
Michael R. Buchalski, Benjamin N. Sacks, Daphne A. Gille, Maria Cecilia T. Penedo, Holly B. Ernest, Scott A. Morrison, Walter M. Boyce
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Abstract

Fossil data are ambiguous regarding the evolutionary origin of contemporary desert bighorn sheep (Ovis canadensis subspecies). To address this uncertainty, we conducted phylogeographic and population genetic analyses on bighorn sheep subspecies found in southwestern North America. We analyzed 515 base pairs of mtDNA control region sequence and 39 microsatellites in 804 individuals from 58 locations. Phylogenetic analyses revealed 2 highly divergent clades concordant with Sierra Nevada (O. c. sierrae) and Rocky Mountain (O. c. canadensis) bighorn and showed that these 2 subspecies both diverged from desert bighorn prior to or during the Illinoian glaciation (∼315–94 thousand years ago [kya]). Desert bighorn comprised several more recently diverged haplogroups concordant with the putative Nelson (O. c. nelsoni), Mexican (O. c. mexicana), and Peninsular (O. c. cremnobates) subspecies. Corresponding estimates of effective splitting times (∼17–3 kya), and haplogroup ages (∼85–72 kya) placed the most likely timeframe for divergence among desert bighorn subspecies somewhere within the last glacial maximum. Median-joining haplotype network and Bayesian skyline analyses both indicated that desert bighorn collectively comprised a historically large and haplotype-diverse population, which subsequently lost much of its diversity through demographic decline. Using microsatellite data, discriminant analysis of principle components (DAPC) and Bayesian clustering analyses both indicated genetic structure concordant with the geographic distribution of 3 desert subspecies. Likewise, microsatellite and mitochondrial-based FST comparisons revealed significant fixation indices among the desert bighorn genetic clusters. We conclude these desert subspecies represent ancient lineages likely descended from separate Pleistocene refugial populations and should therefore be managed as distinct taxa to preserve maximal biodiversity.

© The Author 2016. Published by Oxford University Press on behalf of American Society of Mammalogists. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/ ), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contactjournals.permissions@oup.com
Michael R. Buchalski, Benjamin N. Sacks, Daphne A. Gille, Maria Cecilia T. Penedo, Holly B. Ernest, Scott A. Morrison, and Walter M. Boyce "Phylogeographic and population genetic structure of bighorn sheep (Ovis canadensis) in North American deserts," Journal of Mammalogy 97(3), 823-838, (16 February 2016). https://doi.org/10.1093/jmammal/gyw011
Received: 9 July 2015; Accepted: 11 January 2016; Published: 16 February 2016
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