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The red wolf (Canis rufus): Ancient species, hybrid origin or recent hybrid
Much debate and controversy has surrounded the taxonomy of the red wolf (Canis rufus) in recent years (Nowak, 1992; Wayne, 1992; Henry, 1992; Dowling et al., 1992; etc.). The disputing factions do agree that these canids' present genetic composition has been altered by hybridization with the coyote (Canis latrans). However, disagreement erupts when the discussion turns to the origins of the animal.
Based on an analysis of mtDNA, Wayne and Jenks (1991) suggest a hybrid origin for the red wolf. Dowling et al. (1992) have questioned their conclusions. Roy et al. (1996) similarly hypothesize a hybrid origin based on an analysis of both mtDNA and the analysis of ten microsatellite nuclear loci. Both of these analyses have tested recent (post 1900) specimens where hybridization was already underway. Roy et al. (1996) suggest that unique red wolf alleles should have been found due to finding unique markers in the Mexican wolf (Canis lupus baileyi). However, there is not a long-recognized view that Mexican wolf populations have ever interbred with coyotes. Nevertheless, Roy et al. (1996) report finding a unique mtDNA genotype in Mexican wolves that also exists at a low frequency in coyotes and red wolves from Texas, but that does not occur in other North American gray wolves (Canis lupus). Based on these data they blindly imply that hybridization between Mexican wolves and coyotes had occurred. If this in fact is true, the mexican wolf should be considered a hybrid also. Red wolves have also exhibited wolf genotypes as well as coyote genotypes. Nevertheless, Roy et al. (1996) do state that their genetic analysis cannot readily deduce the precise timing of hybridization nor the true origin of the red wolf and both Wayne and Jenks (1991) and Roy et al. (1996) support continued protection of the red wolf. Wayne (1995) suggests that the red wolf may have had a mtDNA origin similar to that of wolves from Minnesota, Ontario, and Quebec which also possess a high frequency of coyote mtDNA genotypes (Lehman et al., 1991). However, these regions were not historically (or prehistorically, based on the fossil record) ever inhabited by a small unique wolf such as the red wolf. Similarly, both the gray wolf and red wolf, through loss of habitat and population decline in recent times, encountered interspecific mating opportunities with the coyote.
On the other hand, both multivariate and univariate statistical examinations of fossil and modern skulls (Nowak, 1979; Nowak and Federoff, 1996) depict a different picture. The available data indicate that a small distinctive variety of wolf (whether designated as C. rufus or C. lupus rufus, although I prefer the latter) existed in Southeastern North America, in much the same form as now, for at least 700,000 years, and that hybridization between C. rufus and C. latrans began 100 years ago in Central Texas and subsequently spread through much of the former range of the red wolf. Analysis of every available specimen of free-ranging Canis, dating from before the coyote invasion in the region east of the Mississippi River and south of Wisconsin, Michigan, and New York State, does indicate the presence of a small wolf, distinct from the coyote yet showing the statistical consistency of other wolf populations (Nowak and Federoff, 1996; Nowak and Federoff, unpublished data, appendix A). This analysis demonstrates that neither the coyote nor the large gray wolf was historically present in that region. Lawrence and Bossert (1967;1975) suggest that perhaps present-day red wolves may be descendants of an extinct unique subspecies of southern gray wolf. Wayne (1995) also finds this an appealing hypothesis. Nevertheless, the red wolf, even in present hybridized form, is the final repository for these unique genetics and should be preserved.
Literature Cited
Dowling, T.E., B.D. DeMarais, W.L. Minckley, M.E. Douglas, and P.C. Marsh. 1992. Use of genetic characters in conservation biology. Conservation Biology 6:7-8.
Henry, V. G. 1992. Finding on a petition to delist the red wolf (Canis rufus). Federal Register 57:1246-1250.
Lawrence, B. and W.H. Bossert. 1967. Multiple character analysis of Canis lupus, latrans, and familiaris with a discussion of Canis niger. American Zoologist 7:223-232.
Lawrence, B. and W.H. Bossert. 1975. Relationships of North American Canis shown by multiple character analysis of selected populations. In The wild canids, M.W. Fox (ed.), Van Nostrand Reinhold, New York. pp. 73-86.
Lehman, N., A. Eisenhawer, K. Hansen, L.D. Mech, R.O. Peterson, P.J.P. Gogan, and R.K. Wayne. 1991. Introgression of coyote mitochondrial DNA into sympatric North American gray wolf populations. Evolution 45:104-119.
Nowak, R.M. 1979. North American Quaternary Canis. University of Kansas Museum of Natural History Monograph, no. 6, 154 pp.
Nowak, R.M. 1992. The red wolf is not a hybrid. Conservation Biology 6:593-595.
Nowak, R.M., and N.E. Federoff. 1996. Systematics of wolves in Eastern North America. In Wolves of America Conference Proceedings, November 14-16, Defenders of Wildlife, Washington, DC. pp. 187-203.
Roy, M.S., E. Geffen, D. Smith, and R.K. Wayne. 1996. Molecular Genetics of Pre-1940 Red Wolves. Conservation Biology 10:1413-1424.
Wayne, R.K. 1992. On the use of morphologic and molecular genetic characters to investigate species status. Conservation Biology 6:590-592.
Wayne, R.K. 1995. Red wolves: to conserve or not to conserve. Canid News (Newsletter of the IUCN, Canid Specialist Group) 3:7-12.
Wayne, R.K., and S.M. Jenks. 1991. Mitochondrial DNA analysis implying extensive hybridization of the endangered red wolf Canis rufus. Nature 351:565-568.
