For now, he points out, “the data we have presently can’t distinguish between the three hypotheses: that red wolf is a distinctive species but we haven’t found its distinctiveness; that it’s a subspecies and we may not be able [through present genetic techniques] to observe a subspecies of wolves; or that the origin of the red wolf was as a hybrid. I still believe the morphological data can’t be used to exclude that hypothesis.” One morphological approach that might help answer the question would be a study in which gray wolves and coyotes are cross-bred for three generations in a laboratory, and the offspring examined to see whether they resemble red wolves. That, however, would be an expensive undertaking, and no one has offered to do it. Says Wayne, “We don’t know really what coyote-gray-wolf hybrids should look like morphologically. We really need to know that.”
Though Wayne did not declare the red wolf to be a hybrid, opponents of wolf recovery seized upon his studies and called for an end to federal protections for wolves. In 1990, after hearing early reports of Wayne’s work, the Wyoming Farm Bureau Federation petitioned the federal government to delist the gray wolf on the grounds that it was “not a species” and that the Fish and Wildlife Service was “unable to distinguish pure wolves from hybrid wolves.” In 1991, Wayne’s findings prompted the American Sheep Industry Association to petition the Department of the Interior to delist the red wolf on the grounds that it was a hybrid.
The U.S. Department of the Interior’s policy on hybrids is based on something called “the biological species concept,” which holds that a species is a species because it will not breed with members of other species. Species and subspecies are precisely adapted to local conditions, and “the biological species concept” implies that, by introducing genes that evolved in other settings, we may reduce a creature’s ability to survive, or cause it to have new and detrimental effects on its environment. The Endangered Species Act, which drives the conservation of plants and animals in the United States, was written with this species concept in mind, and it does not accept hybridization. In a series of rulings, Department of the Interior solicitors have refused to grant Endangered Species Act protections to hybrids. A proposal to add to the California population of southern sea otters by introducing sea otters from the Alaskan subspecies was rejected because of the hybridization issue. In 1981, the Fish and Wildlife Service refused to allow the last few dusky seaside sparrows—all of which were males—to be bred with females of another subspecies, Scott’s seaside sparrow, even though it meant the certain extinction of the dusky seaside sparrow. The Fish and Wildlife Service refused to allow crossing of the Mississippi sandhill crane with the Florida sandhill crane, despite the presumption that the two subspecies had only been separated for perhaps two hundred years. The Mexican duck was removed from the endangered-species list because it hybridized with an expanding mallard-duck population. The Amistad gambusia and the Tecopa pupfish were removed from the endangered-species list because all the surviving individuals carried the genes of other fish species.
As a foundation for wildlife conservation, “the biological species concept” can be slippery, because it presumes species are fixed and unchanging. An evolutionary view holds that all species are in the process of change, and that hybridization is one of the possible ways species adapt to changing environments. In fact, the geographical barriers that give rise to subspecies can vanish through natural processes such as climate change, flood, or erosion, and subspecies may suddenly begin interbreeding. Intergrades between subspecies often appear where their ranges come together. Even different species can and will interbreed: species of mice, voles, and frogs have interbred in the wild; fish frequently breed across species lines and intergrade at the edges of their ranges, so that it is difficult to tell which species one has in hand; plant biologists long ago recognized that plant species interbreed, and that new species often form through hybridization in the wild.
Taxonomists, the biologists responsible for naming species and evaluating the evolutionary links between them, have tended both to lump and to split species over the facts of hybridization. In recent years, taxonomists have lumped together red- and yellow-shafted flickers, Bullock’s and Baltimore orioles, and Mexican and mallard ducks because they so extensively interbreed. At the same time, they left separate black and mallard ducks, lazuli and blue buntings, and black-headed and rose-breasted grosbeaks, even though these frequently interbreed. Taxonomists are finding it more and more necessary to deal with the issue of hybridization and to bestow names on the basis of selectivity of mating, width of hybrid zones (the range over which two species mate and form hybrids), and the persistence of physical characteristics among the offspring of these matings.
The presumption against hybrids is especially strong when the hybridization is a result of human activity. We practice a kind of misanthropy, regarding coyote genes in wolf blood, or genetic depression due to inbreeding as stains of our own meddling and conceit. At best, we fear we have altered the course of evolution, something we believe mere humans should never do—but something we do nonetheless on a massive scale. At worst, we fear we have made the wolves into human artifacts. It may be that we choose our hybrids with a view to how much other humans have been party to their creation, that the traits we fear in such creatures are not biological but moral.
To refuse protection to hybrids may in some cases amount to declaring that evolution must stop at the present. Says Wayne, “Species are not static. It’s clear from the paleontological record that species are not set. They change.” Increasingly, biologists argue that we must protect the biological processes, not just the species that result from them. What is important, Nowak believes, is to focus on whether the sharing of genes alters the organism’s interactions with the environment. “One hundred percent of the gray wolves on Isle Royale have coyote mitochondrial DNA,” he says. “And yet all of the people I’ve spoken with say they are 100 percent wolflike, morphologically and behaviorally.” The genetic technique cannot tell whether the hybridization occurred once thousands of years ago or many times recently. Nor can it tell whether hybridization has affected an animal’s fitness. Coyote genes may not have altered the red wolf in ways that matter to the wild landscape. What ought to count is not whether we have inadvertently lowered a reproductive barrier, but whether the wolves perform the same functions in the wild, and whether evolution still goes on shaping the animal as it did before.
There is increasing inclination at the U.S. Department of the Interior to adopt a more liberal hybrid policy. The federal government rejected the Wyoming Farm Bureau Federation petition to delist the wolf in part on the grounds that “mitochondrial DNA does not function in the production of observable traits” that are acted upon by evolution, and so it could not define the red wolf as a hybrid. It cautioned that Wayne’s results constituted the first such look at wolves and were “subject to future reinterpretarions.” In 1992, the Department of the Interior denied the Sheep Industry Association’s petition, saying, “Several different species concepts, including a revised biological species concept, are now dominating taxonomic thinking. These alternative concepts incorporate the idea of limited genetic interchange with other recognized species. The service is currently reviewing and evaluating possible alternative species concepts.”
Until there is either a new hybrid policy or a consensus that the red wolf is a legitimate species, the fate of the red wolf will remain uncertain. Some biologists and wildlife officials will continue to believe the red wolf is an artifact and therefore not worthy of reintroduction. Phillips recalls a meeting to discuss canid conservation at Fossil Rim, Texas: “Every time the red wolf came up, there’d be a nervous laugh, and people would move on to other things.” People who were avid about the reintroduction of gray wolves in Yellowstone, he says, would get up and leave the room when discussion turned to the red wolf.
The new genetic techniques were bound to create controversy. Molecular genetics is an upstart science weighted with technical terms t
hat field researchers and ecologists find perplexing. Few of them know how the technology of reading gene sequences works, and when a geneticist speaks to them of “phylogenetically distinct mitochondrial DNA genotypes,” a fog of unfamiliarity falls over the conversation.
It is not just a matter of unfamiliar terms, but of styles. The morphologist looks at color and texture, line and distance. He or she handles the specimen, runs a finger over the ridges and hollows of a skull, smooths out the fur of a museum specimen, imagines the eye that once looked out of the socket, perhaps feels the heart that once beat inside the skin. The geneticist, on the other hand, hardly ever sees the organism, or even a recognizable artifact of the living creature. What the geneticist sees are test tubes, beakers, and stacks of radioactive chemicals in acrylide gels. It is a long and blinding jump from the tactile and visual world of morphology to the abstraction and quantification of the molecular-genetics laboratory, a jump traditional scientists may be unprepared to make.
Clearly, the genetic techniques are useful. Says Wayne, “The techniques of molecular genetics promise new kinds of insights into the lives of wolves.” One of the most exciting is the possibility of telling exactly how the wolves in an area are related to one another. Wayne has used a technique called “genetic fingerprinting” to look at the paternity and movement of individuals and packs in Alaska and Minnesota. Wayne analyzed mitochondrial DNA from three clusters of wolf packs and counted the DNA patterns shared between individuals. He judged from their similarities and differences which wolves were brothers and sisters, and which were unrelated. The technique can help tell which individuals have dispersed from other packs, and whether there is a sex bias in dispersal. Ultimately, the techniques may be used to show exact genealogical relationships among wolves in a broad area.
The new science produces results. One of these could be the revision of two centuries of taxonomic work and the renaming of plants and animals based upon comparisons of their genetic patterns. Already, genetics and morphology seem to be moving together toward a consensus that would reduce the number of subspecies of North American gray wolf from twenty-four to five. Early collectors gathered specimens on the basis of color or size, presuming that geographic differences inevitably led to subspecific differences. Our present classification may have been colored by subjective things that occurred to collectors years ago. Wayne says, “You can imagine the first explorers when they walked through Florida and saw a couple of black wolves, and of course that became a subspecies.” So subspecies tended to multiply. In 1944, Edward Goldman listed twenty-three subspecies of gray wolf in North America. In 1981, Raymond Hall listed twenty-four (see Appendix 3 for the list). Subspecies are supposed to reflect geographic boundaries, but, given the demonstrated migration of radio-collared wolves, the geographic boundaries assumed by earlier taxonomists appear to be less and less meaningful. There has been growing agreement that not all these subspecies are valid, and this new view has tended to divide the North American subspecies north and south, roughly along the Canada-United States border.
Nowak compared the measurements of skulls of wolves north of the border with wolves south of the border. His analysis showed differences between the northern and southern subspecies, and led him to conclude that only five subspecies seemed legitimate. If other taxonomists agree with Nowak, a new list of wolf subspecies might look like this: Canis lupus occidentalis would be the northern wolf and would include the seven subspecies of Alaska, western Canada, and northern Montana. Canis lupus nubilus would be the southern subspecies, and it would encompass the twelve subspecies that range from southeastern Canada and southern British Columbia east to Texas and the Great Lakes, central Quebec, southern Greenland, and Baffin Island. Canis lupus arctos would lump together three subspecies of the Arctic Islands and northern Greenland. Canis lupus baileyi of Mexico and the American Southwest and Canis lupus lycaon of southeastern Canada and the northeastern United States would also be recognized as legitimate subspecies.
The most important characteristic Nowak found separating the subspecies was size, but there was no gradual change due to geographic range. The biggest wolves, for example, were from Alberta, not from Alaska. Nowak found that hudsonicus, the wolf living on the western side of Hudson Bay, manningi, the wolf of Baffin Island, and beothucus, the extinct wolf of Newfoundland, all fit nicely into the newly defined nubilus. Asks Nowak, “How can I refer animals way up on Newfoundland and Baffin Island to the southern group of species?” The answer seemed to be that successive waves of immigration of wolves from Asia pushed earlier arrivals east and south. “In Pleistocene, we had several reinvasions of North America via the land bridge. The subspecies furthest south—baileyi and lycaon—probably represent the earliest invasion. Then nubilus. Then, finally, I think the continent was invaded by fairly large wolves from ice-free refugia when the ice retreated.”
The analysis seemed to Nowak to confirm the legitimacy of the red wolf, Canis rufus, as a separate species. He looked also at Eurasian subspecies of gray wolves and concluded that there was evidence to support five subspecies: Canis lupus lupus from Europe to Russia, Canis lupus albus in extreme northern Eurasia, Canis lupus pallipes from Israel to India, Canis lupus cubanensis in the Caucasus, Turkey, and Iran, and Canis lupus communis in the Ural Mountains region. He compared the three southernmost subspecies, pallipes, baileyi, and rufus. He found that baileyi stood apart, “but, despite one million years in time and ten thousand miles in space,” he says, “we do have a tenuous overlap between pallipes and rufus. Here is evidence of this ancient migration of the ancestral wolf to Asia.”
Wayne also surmised that there were fewer than twenty-four subspecies of gray wolf. “It was interesting to me,” he says, “that subspecies had been defined that didn’t correspond to any geographic boundaries. I suspected many of these subspecies didn’t express real genetic boundaries.” Genetic techniques had been used to inquire whether a subspecies is truly a separate group. DNA analyses have shown, for example, that deer mice that live near each other have similar gene sequences, but deer mice that live a long way from one another don’t. That suggests that the distant populations are no longer interbreeding and may be regarded as distinct subspecies.
Wayne performed an analysis which showed a different pattern with canids. He says, “We found thirty-two different coyote genotypes in different localities. In each of the localities there were multiple genotypes, and we found the same genotypes in different sites.” There seems to be mixing of genes of coyotes on a continental scale. With wolves, there are a few ubiquitous genotypes that are found more or less everywhere, reflecting gene flow over the continent. Wayne explains, “A wolf can disperse five hundred miles; one researcher estimates the zone of hybridization [the range in which dispersing individuals may form hybrids] is fifty times the dispersal distance, so that means wolves have a hybridization zone almost as big as the continent.”
Wayne found evidence of five genotypes in the wolves of North America and seven in the wolves of the Old World. The clusters he came up with seem to converge with the clusters Nowak has found. “We did find evidence that the Mexican wolf had a unique genotype,” says Wayne. “And we found some evidence that Alaskan wolves are different from wolves in the Northwest Territory. We didn’t sample wolves in northeastern Canada. But we’re coming close to agreement.”
Such a convergence suggests that traditional morphology and modern genetics may yet make peace. “They’ve been seen to be at odds,” Wayne says, “but the two complement each other.” And as time goes on, he expects the two approaches to change the way we view species. “Our museum collections are based around the idea of a type,” he says. “The truth is, there is immense variability, and somehow you’ve got to take into account the variability within a species.” In some cases, he expects the genetic techniques to increase the recognized number of subspecies. “Smaller species with more local distribution, like pocket gophers and deer mice, will show more variation and more differentiation. O
n balance for the smaller species, molecular-genetics techniques probably will define more subspecies.
“But for highly mobile species, like wolves, the genetic information will show the high mobility has stifled any great degree of genetic variability,” because wolves share their genes over such a broad range. So genetic techniques may end up reducing the number of subspecies in wolves.
Clearly, the genetic techniques are going to change the way we define species and subspecies. This redefinition poses real challenges to the way we look at conservation. We already argue over whether it is legitimate to try to save subspecies and local populations. When we start thinking about conserving the whole genetic range of a species, the task of conservation will grow much larger. “We’re down to the point where every individual is genetically distinct,” says Rolf Peterson. “So how are we going to save the whole gene pool?”
The new knowledge will urge us to integrate the saving of genes with the saving of ecological functions. Whereas today most people view conservation in terms of saving individual animals, future conservationists will have to think about saving ecosystems, and ecosystems will have to be defined in terms of the genes that constitute them. When we consider the genetic variety necessary to maintain an ecosystem, we will face new levels of complexity and conflict in management.
And how shall we accommodate distinctions we have long made—that the buffalo wolf of the Great Plains is distinct from the timber wolf of Minnesota, or the tundra wolf of Alaska is different from the wolf of the Alaskan interior? Zoos still register their wolves by subspecies, and breeders of wolves cling to and value these distinctions. Conservationists champion local varieties as unique and irreplaceable. Those who oppose reintroductions argue that the subspecies being reintroduced never inhabited the recovery area. Revision of the systematics of wolves is bound to confute many of these distinctions, and discomfort many of those who make them. It will add to the already contentious claims we make about the identities of wolves.
The Company of Wolves Page 23