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Admixture in Two Proposed Wolf Species May Have Conservation Implications

NEW YORK (GenomeWeb) – North America's eastern and red wolves do not appear to represent distinct species, but are hybrids between the coyote (Canis latrans) and gray wolf (C. lupus) species, according to a study appearing online today in Science Advances.

Researchers from the US, China, and Israel sequenced the genomes of 28 canids, including gray wolves, eastern wolves, red wolves, and coyotes from North America, gray wolf representatives from India, Iran, China, and Mongolia, a golden jackal, and three domestic dogs. They found that patterns in the genomes did not support unique ancestry for the eastern and red wolves, but rather pointed to a gradient of gray wolf and coyote ancestry in the eastern and red wolf genomes.

Consequently, the researchers contend that there is insufficient evidence for removing gray wolves from the list of animals protected under the Endangered Species Act.

"The US Fish and Wildlife Service has argued that the presence of the eastern wolf, rather than the gray wolf, in [the Great Lakes and eastern United States] is ground for removing ESA protection (delisting) from the gray wolf across its geographic range," senior author Robert Wayne, an ecology and evolutionary biology researcher at the University of California at Los Angeles, and his co-authors wrote.

Instead, the investigators called for conservation strategies that consider and encompass the admixture that exists across the continent's wild canids. "We argue strongly for a less typologically oriented implementation of the ESA that allows interim protection of hybrids while encouraging the restoration of historic patterns of variation through habitat protection," they wrote.

While viewing the eastern and red wolves as distinct species has facilitated protection of the red wolf in the southeastern US, the study's authors explained, the designations have been used as rationale for curbing eastern and gray wolf protections, narrowing each animal's perceived historical range.

The researchers used Illumina's HiSeq platform to sequence the 28 canids — including eastern/Great Lakes wolves, possibly from the C. lycaon species, and three red wolves (C. rufus) from a captive breeding program in the US — to between four and 29-fold coverage. They mapped these canid reads to the domestic dog reference genome, uncovering more than 5.4 million SNPs following filtering and quality control steps. In their subsequent analyses, those variants clustered the gray wolves and coyotes separately, though genetic variation existed within the groups, consistent with geographical separation within each species. The North American and Eurasian wolves differed genetically, for example, with coyote ancestry turning up in the gray wolves from North America.

In contrast, both the red wolves and eastern wolves showed signs of admixture, the researchers reported. The proportion of variants stemming from wolf ancestors was greatest in eastern wolves from the Great Lakes region, but dropped off in wolves from Canada's Algonquin provincial park and in red wolves, which had higher coyote ancestry.

Their results suggest that coyote-gray wolf mixing occurred in the Southeastern US hundreds of years ago, while admixture in the Great Lakes region seems to have stemmed from interactions between coyotes arriving in the area in the 1920s and dwindling gray wolf populations.

"We found no evidence for an eastern wolf that has a separate evolutionary legacy," Wayne said in a statement, noting that the "gray wolf should keep its endangered species status and be preserved because the reason for removing it is incorrect." He and his team also suggested that an appreciation of admixture between wolves and coyotes could offer clues for managing and/or reintroducing threatened canid populations.