A molecular genetic analysis of hybridization between two species of deer (Odocoileus) in western Canada

Hughes, Glenys Anne (1990) A molecular genetic analysis of hybridization between two species of deer (Odocoileus) in western Canada. Masters thesis, Memorial University of Newfoundland.

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Abstract

Hybridization between two species of deer (Odocoileus) in western Canada has been postulated for many years. Mitochondrial and nuclear components of the genomes of deer from this and other regions in North America were analyzed to test whether these deer constitute reproductively isolated species or whether interspecies genetic exchange has occurred by hybridization. -- The polymerase chain reaction (PCR) was used to amplify a 359 base pair fragment of the mitochondrial cytochrome b gene from 81 white-tailed deer (O. virginianus), mule deer (O. hemionus hemionus), and Sitka black-tailed deer (O. hemionus sitkensis). Direct DNA sequencing of a 302 base pair block of the PCR-amplified products revealed 34 variable nucleotide positions. These variants define 13 distinct mitochondrial DNA (mtDNA) sequence genotypes. Twelve of these are confined to one or the other species: five genotypes were found only in white-tailed deer and seven only in mule deer or black-tailed deer. In only one instance is a genotype shared between species: a single deer that had been identified as a mule deer possessed a white-tailed deer-type mtDNA. -- Allelic variants at the albumin locus also distinguish the two species. Of 53 animals sampled from British Columbia, Alberta, and Saskatchewan, 25 white-tailed deer and 27 mule deer were homozygous for slow and fast albumin alleles, respectively. Only one animal showed the heterozygote albumin pattern characteristic of hybrid deer. This individual is the same mule deer that possessed an mtDNA genotype found otherwise only in white-tailed deer. -- These data suggest there is little genetic introgression between mule deer and white-tailed deer in western Canada. Similar findings have been reported for Odocoileus in Montana, but high levels of hybridization have been documented between the same species in west Texas. Habitat disturbance and mating behaviour are factors that may affect the frequency and direction of hybridization in different localities. -- Phenetic and cladistic analyses of sequence differences among white-tailed deer, mule deer, and black-tailed deer reveal a discordance between mtDNA genotype and species affinity. Interspecies hybridization, random phylogenetic sorting of mtDNA lineages, and differential rate of mtDNA evolution are considered as hypotheses to explain the relationships among mtDNA genotypes of these species.

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