Genetic Relationships between Mule Deer and White-Tailed Deer in Montana

Abstract

We used protein electrophoresis of serum albumin and restriction endonuclease analysis of mitochondrial deoxyribonucleic acid (mtDNA) to characterize gene flow between mule deer (Odocoileus hemionus) and white-tailed deer (0. virginianus). Mitochondrial DNA and serum albumin appear to be distinct between mule deer and white-tailed deer in Montana, suggesting that interspecific gene flow is not extensive. J. WILDL. MANAGE. 52(2):320-328 Protein electrophoretic studies have revealed 2 serum albumin alleles in white-tailed and mule deer populations with a different allele predominating in each species (McClymont et al. 1982, Smith et al. 1984, Stubblefield et al. 1986). Electrophoretic analyses of 17-35 protein loci have shown that genetic distances between whitetailed and mule deer in North America are similar to those for other congeneric species or subspecies (Baccus et al. 1983, Gavin and May 1988). However, genetic distances between white-tailed deer from South America and the southeastern United States are greater than those between mule and white-tailed deer, which may indicate that intraspecific genetic variation is substantial in deer (Smith et al. 1986). Matings of mule deer or Columbian blacktailed deer (0. h. columbianus) with white-tailed deer in captivity may result in fertile or sterile hybrids (Cowan 1962, Whitehead 1972, Wallmo 1981). Interspecific hybridization in natural populations of white-tailed deer and mule deer has been reported in British Columbia (Cowan 1962), Alberta (Wishart 1980), Texas (Carr et al. 1986, Stubblefield et al. 1986), and other areas (Kramer 1973). The occurrence of a wild, hybrid female carrying 3 fetuses in Alberta (Wishart 1980) indicates that wild hybrids may breed successfully. Genetic data from protein electrophoresis and 'Present address: Department of Biology, Yale University, New Haven, CT 06511. This content downloaded from 207.46.13.40 on Wed, 30 Mar 2016 05:34:35 UTC All use subject to http://about.jstor.org/terms J. Wildl. Manage. 52(2):1988 MONTANA DEER GENETICS * Cronin et al. 321 mtDNA restriction enzyme analyses have been used to identify genetic divergence and introgressive hybridization between species and subspecies of deer (Carr et al. 1986, Smith et al. 1986, Gavin and May 1988). Mitochondrial DNA is maternally inherited without recombination and species-specific restriction fragment length polymorphisms may be used to identify the female parentage of hybrids (Avise 1986). Data from protein electrophoresis may allow estimation of the extent of nuclear gene flow between species. In areas where mule and whitetailed deer coexist, species-diagnostic mitochondrial and nuclear genetic markers may be used to determine how often and under what conditions hybridization occurs. Such genetic data may be used by managers to institute harvest regimes or habitat manipulations which minimize hybridization or achieve the desired distribution of species. White-tailed and mule deer occur sympatrically over much of Montana, although they generally use different habitats and are managed as separate species (Martinka 1968, Mackie 1981, Swenson et al. 1983). In parts of Montana whitetailed deer have come into contact with mule deer after range expansion over the last few decades, increasing the possibility of hybridization and resource competition (Martinka 1968). We analyzed the variation in serum albumin and mtDNA in sympatric and allopatric populations of mule deer and white-tailed deer from several geographic areas. Our objectives were to describe geographic patterns of variation and to test the hypothesis that mule deer and whitetailed deer in Montana are genetically distinct and reproductively isolated species. Thanks are extended to R. J. Mackie, Montana State University; D. A. Palmisciano, D. F. Pac, and L. J. Ellig, Montana Department of Fish, Wildlife and Parks; J. V. Spignesi, Connecticut Department of Environmental Protection; L. R. Kaeding, U.S. Fish and Wildlife Service; E. A. Rollor, University of Georgia; P. M. Wilson, R. L. Kahlenbeck, D. G. Williams, E. Arnett, and the many hunters and biologists who supplied samples for this study. S. M. Carr, V. Geist, W. D. Wishart, K. T. Scribner, R. L. Honeycutt, and R. DeSalle provided helpful comments. J. F. Chavez and S. K. Watters provided technical assistance and J. R. Powell provided lab facilities for part of the analysis. Funding was provided by the School of Graduate Studies, Montana State University, Bozeman. METHODS Brain, kidney, liver, or muscle samples (50100 g) were collected from 156 white-tailed and 98 mule deer in Montana, and 2 mule deer in Wyoming during the 1984-86 fall hunting seasons. All tissues were useable for mtDNA and serum albumin analyses although brain, kidney, and liver yielded more mtDNA/g and were collected when available. Collections were made by biologists at game check stations and hunters who placed tissues in plastic bags and recorded the species and location of kill. Tissues were kept cool until frozen at -20 C, usually <24 hours after death. The white-tailed deer and some of the mule deer were from areas of sympatry or parapatry, and the mule deer from northeastern Montana (Fig. 1) were approximately 30 km from known white-tailed deer concentrations. For comparisons with allopatric populations, tissues were obtained from 5, 5, 7, and 1 whitetailed deer from Georgia, Illinois, Connecticut, and Pennsylvania, respectively; 4 mule deer from Colorado; and 3 Sitka black-tailed deer (Odocoileus hemionus sitkensis) from Kodiak Island, Alaska. Serum albumin genotypes were determined for all 281 samples by polyacrylamide gel electrophoresis (McClymont et al. 1982). Two modifications of this method were made that gave better resolution of albumin bands: the gel buffer was 1.5 M tris[hydroxymethyl]aminomethanehydrochloric acid, pH 8.8, and the stain was Coomassie blue R250. Mitochondria were isolated from 10 to 25 g of tissue by differential centrifugation (Powell and Zuniga 1983). The mitochondrial pellet was treated with deoxyribonuclease-1 (Watanabe et al. 1985). Mitochondrial lysis and purification . 0o 8 .8 o C *D * 0 N *A OD OA 00 -. o.oo O ,B .* o o /C OCgc O oC o 0B, *A OC .8 *A 0.