Wolves and humans share one of the most multifaceted and transformative relationships in the animal kingdom. These wild canines provided the initial stock for "man's best friend," the domestic dog, but wolves have also been demonized and over-hunted, especially over the past 150 years, which led to their near-extinction in the continental US by the mid-20th century.
The recent reintroduction of wolves to American wilderness regions has positively transformed ecosystems and restored an iconic predator to its natural range. But as wolves bounce back in areas like Yellowstone National Park, the Great Lakes, and the South, debates have been brewing about the possibility of removing the gray wolf from protection under the Endangered Species Act, which would make it legal to hunt them again.
In particular, the US Fish and Wildlife Service has been pushing a plan to delist gray wolves from ESA protection across their entire North American range by 2017. Some local gray wolf populations have already been delisted from federal protection and handed over to state management, but these cases have met with opposition, and some have been overturned.
One of the most complex issues raised by the US Fish and Wildlife Service's move to roll back protection on wolves is the thorny nature of wolf ancestry itself. Gray wolves, red wolves, eastern wolves, or Mexican wolves are all treated as distinct species, but in reality, wild canines aren't exactly concerned with maintaining their unique pedigrees. There is all manner of genetic wiggle room between these species, and hybridization with domestic dogs and coyotes is common.
Protecting hybrids of endangered and non-endangered species is a notoriously murky area under the ESA, so the taxonomical classification of North American wolves has real world consequences for their conservation.
In a new paper published Wednesday in Science Advances, UCLA evolutionary biologist Robert K. Wayne and his colleagues present evidence confirming the mixed ancestry of red and eastern wolves, which the authors argue has far-reaching implications for conservation policy.
By conducting whole-genome sequence analysis on 28 canids—including gray wolves, red wolves, eastern wolves, coyotes, and even domestic dogs—the team found that the red wolf is about 25 percent gray wolf and 75 percent coyote, while the eastern wolf is about 50 to 75 percent gray wolf, and roughly one quarter coyote.
Okay, so there's been some free love between gray wolves and coyotes over the past century, resulting in hybrid lineages. What's the big deal? Well, take the example of the eastern wolf, recognized as endangered by the USFWS. The fact that this wolf's supposed historic range overlaps with the gray wolf's range has been used by the USFWS as grounds for delisting the gray wolf.
"Essentially, the presence of the eastern wolf, rather than the gray wolf, in the eastern United States would cause the original [ESA] listing to be annulled," the authors point out. "With the exception of the Mexican wolf, the gray wolf would be delisted (lose protection) from its entire North American range under the proposed USFWS rule change."
"These differing consequences of species listing, despite the possibility of similar admixed origin, provide a marked example of how taxonomy can both protect and threaten endangered species under the ESA."
I asked Wayne if this ambiguity regarding hybrid populations is limited to wolves, or if many mixed species are facing similar conservation hurdles due to their ancestry. "I do think it is a general problem," he said, "as the [ESA] protects not only species, but subspecies, and distinct population segments which may interbreed with non endangered conspecifics."
There is no "one-size-fits-all approach" to managing hybrid populations, Wayne said in another recent paper, published in Molecular Biology. But the example of North American wolves suggests that the USFWS strict focus on taxonomical relationships is "antiquated" and "Victorian," according to the Science Advances study.
Recent breakthroughs in genomics have reaffirmed that wild populations are always in flux and don't easily fit constrictive categories. Moreover, the pressures of climate change, habitat loss, and other anthropogenic activity play a major role in shaping hybridization. For instance, the steady extermination of American wolves by humans, beginning in the late 1800s, may have provoked wolves desperate to find a mate to breed with coyotes instead.
"Species and taxonomic concepts are varied, complex, and difficult to apply in practice," the team said. "Of greater importance are the preservation of evolutionary and ecological processes and the role of an endangered taxon in this dynamic. Admixture is one critical example of a process that may enhance adaptation and evolution in the rapidly changing environment of the modern world."