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Ephemeral Pleistocene woodlands connect the dots for highland rattlesnakes of the Crotalus intermedius group

Authors

  • Robert W. Bryson Jr,

    Corresponding author
    1. School of Life Sciences, University of Nevada, Las Vegas, 4505 Maryland Parkway, Las Vegas, NV 89154-4004, USA
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  • Robert W. Murphy,

    1. Centre for Biodiversity and Conservation Biology, Royal Ontario Museum, Toronto, ON M5S 2C6, Canada
    2. State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, The Chinese Academy of Sciences, Kunming 650223, China
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  • Matthew R. Graham,

    1. School of Life Sciences, University of Nevada, Las Vegas, 4505 Maryland Parkway, Las Vegas, NV 89154-4004, USA
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  • Amy Lathrop,

    1. Centre for Biodiversity and Conservation Biology, Royal Ontario Museum, Toronto, ON M5S 2C6, Canada
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  • David Lazcano

    1. Laboratorio de Herpetología, Universidad Autónoma de Nuevo León, San Nicolas de los Garza, Nuevo León CP 66440, Mexico
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Robert W. Bryson Jr, School of Life Sciences, University of Nevada, Las Vegas, 4505 Maryland Parkway, Las Vegas, NV 89154-4004, USA.
E-mail: brysonjr@unlv.nevada.edu

Abstract

Aim  To test how Pleistocene climatic changes affected diversification of the Crotalus intermedius species complex.

Location  Highlands of Mexico and the south-western United States (Arizona).

Methods  We synthesize the matrilineal genealogy based on 2406 base pairs of mitochondrial DNA sequences, fossil-calibrated molecular dating, reconstruction of ancestral geographic ranges, and climate-based modelling of species distributions to evaluate the history of female dispersion.

Results  The presently fragmented distribution of the C. intermedius group is the result of both Neogene vicariance and Pleistocene pine–oak habitat fragmentation. Most lineages appear to have a Quaternary origin. The Sierra Madre del Sur and northern Sierra Madre Oriental are likely to have been colonized during this time. Species distribution models for the Last Glacial Maximum predict expansions of suitable habitat for taxa in the southern Sierra Madre Occidental and northern Sierra Madre Oriental.

Main conclusions  Lineage diversification in the C. intermedius group is a consequence of Pleistocene climate cycling. Distribution models for two sister taxa in the northern and southern Sierra Madre Occidental and northern Sierra Madre Oriental during the Last Glacial Maximum provide evidence for the expansion of pine–oak habitat across the Central Mexican Plateau. Downward displacement and subsequent expansions of highland vegetation across Mexico during cooler glacial cycles may have allowed dispersal between highlands, which resulted in contact between previously isolated taxa and the colonization of new habitats.

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