Taxonomic Status and Genetic Purity of Columbian White-Tailed Deer

Abstract

We evaluated the taxonomic status of the endangered Columbian white-tailed deer (Odocoileus virginianus leucurus) using allozyme data from 35 electrophoretic loci. Columbian white-tailed deer and northwest white-tailed deer (0. v. ochrourus) from 5 locations in Oregon and Washington, northern woodland white-tailed deer (0. v. borealis) from 1 location in New York, Columbian black-tailed deer (0. hemionus columbianus) from 3 locations, and Rocky Mountain mule deer (0. h. hemionus) from 4 locations in the Pacific Northwest were included in the analyses (n = 362). Calculation of Nei's (1971) genetic distance (D) among these 5 taxonomic units indicated that the Douglas County, Oregon population of Columbian whitetailed deer may not be sufficiently different in allelic frequencies from northwest white-tailed deer in eastern Oregon and Washington (D = 0.003) to be categorized as a different subspecies. The genetic distance between Columbian white-tailed deer sampled on or near the Columbian White-tailed Deer National Wildlife Refuge (CWDNWR) in southwestern Washington and northwest white-tailed deer from eastern Oregon and Washington was greater (D = 0.010). However, even this genetic distance may not warrant separate subspecific status for these populations. In addition, 6 of 33 Columbian white-tailed deer sampled on or near CWDNWR possessed alleles at 2 of 3 diagnostic loci characteristic of black-tailed deer, confirming observations that hybridization between these species has led to a flow of black-tailed deer genes into this endangered subspecies. J. WILDL. MANAGE. 52(1):1-10 The list of endangered and threatened organisms maintained by the U.S. Department of Interior consists of species and subspecies as specified in the Endangered Species Act of 1973. The assignment of populations to the appropriate subspecies aids the identification and ultimate conservation of unique genetic resources (Myers 1979) and alerts managers about the potential similarity or dissimilarity of genetic stocks (Stromberg and Boyce 1986). The endangered Columbian white-tailed deer is found in only 3 locations in the Pacific Northwest (Fig. 1); it co-occurs with black-tailed deer in each of these areas (Smith 1981). The nearest populations of white-tailed deer are 300 km east in Oregon and Washington (Fig. 1). The original taxonomic description of the Columbian white-tailed deer was published by Douglas (1829). The description was based on coloration and measurements of external morphology of 1 specimen shot, but not preserved, in what is now Douglas County, western Oregon (Douglas 1914:223-224). Douglas' designation of these deer as distinct from those previously described has never been examined quantitatively. The taxonomic status of Columbian whitetailed deer is relevant to their future management. Obviously, if Columbian white-tailed deer are not sufficiently different from other whitetailed deer, then there would not be an endangered subspecies of white-tailed deer in the Pacific Northwest. Alternatively, if 1 or 2 of the 3 existing populations prove not to be Columbian white tailed deer, then the entire subspecies would consist only of the remaining population(s). In either case, management of the populati ns now designated as Columbian whitetailed deer probably would change. Columbian white-tailed deer may interbreed with mule deer (Gavin 1984). Evidence for hybridization in the wild consists of observed mating b havior (but not copulations) between these species (Suring 1974) and observations of appar n hybrids (Davison 1979). Cowan (1962) obtained offspring from crossing a black-tailed male with a white-tailed female, but concluded these individuals were infertile after backcrosses failed to produce offspring; these backcrosses were made between closely related individuals. A male Columbian white-tailed deer repeatedly b d successfully with a female black-tailed deer in captivity in Oregon to produce hybrids, which later produced young of their own (W. O. Lightfoot, Oreg. Dep. Fish and Wildl., pers. commun.). Whitehead (1972) also obtained fertile offspring from crossing captive white-tailed deer and black-tailed deer. Allozymes, which are enzymes that differ in electrophoretic mobility as a result of allelic dif-