Evaluating the Extent of Hybridization between Mule and White-tailed Deer in Western Canada

• Author / Creator

  Russell, Ty

• Mule deer (Odocoileus hemionus) are endemic to a wide variety of habitats in western North America, many of which are shared in sympatry with their closely related sister-species
  white-tailed deer (O. virginianus). Hybridization of mule and white-tailed deer has historically
  been observed on a semi-regular basis throughout this range. Close monitoring of this hybrid
  system continues to be a priority among contemporary evolutionary biologists because (a)
  hybridization is a volatile evolutionary phenomenon, with potential outcomes ranging from
  adaptive introgression to local extinction, (b) deer are ecologically, economically, and
  culturally significant species, and (c) chronic wasting disease (CWD) currently poses a threat
  to farmed and wild cervid populations in western Canada and northern United States. CWD
  is a communicable, fatal, neurodegenerative disease similar to scrapie in sheep and bovine
  spongiform encephalopathy in cattle. Molecular ecological studies have confirmed the
  presence of hybrids in various regions of species overlap, including Alberta, Montana, and
  Texas, but a lack of detection power has limited their identification abilities to the earliest,
  most admixed generations. Furthermore, female F1 hybrids can sometimes retain fertility,
  giving rise to the possibility of advanced-generation backcrosses, which require considerable
  diagnostic power to be reliably identified. In this thesis, I interrogated the Alberta region of
  the hybrid zone with the goals of (a) better characterizing its current state and evolutionary
  trajectory and (b) determining whether hybridization events provide an opportunity for CWD
  transmission to bridge the species gap. To answer these questions, I first developed a SNP
  assay using 40 species-discriminating loci to improve upon the previously available
  molecular methods of hybrid identification. After assessing its utility and efficacy through
  analysis of simulated hybrid populations, I used it to conduct a comprehensive survey of wild deer populations in western Canada. To investigate whether hybridization facilitates
  interspecific CWD spread, I designed sampling strategies to compare hybridization rates
  between infected and uninfected deer. We observed overall hybridization rates of 0.3-1.1%,
  slightly lower than reported elsewhere in the greater hybrid zone. The admixed individuals
  are independent of geographical factors and no significant association between hybridization
  and CWD infection status was found. Although the two species often exist in sympatry and
  share similar diets and life history traits, interspecific gene flow appears to be prevented by a
  number of pre and postzygotic barriers to reproduction, including fine-scale habitat
  segregation and severe underdominance of hybrid offspring. Here, I build upon past studies
  of introgressive hybridization of deer in Alberta by increasing hybrid detection power,
  expanding sample sizes, and providing a new molecular resource applicable to future
  research. This comprehensive, robust, and current assessment of the circumstances of
  hybrids in wild populations will inform stakeholders of patterns of contemporary hybridization
  so they may shape future research and policies accordingly.

• Subjects / Keywords

  • white-tailed deer
  • mule deer
  • hybridization
  • introgression
  • chronic wasting disease

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-mds5-dw65

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.