Report: Red wolves, Mexican gray wolves are distinct species, subspecies

Joseph Travis, Travis, the Robert O. Lawton Distinguished Professor of Biological Science at Florida State.

A yearlong study chaired by a Florida State University professor indicates the red wolf is a distinct species in the wolf family and the Mexican gray is a distinct subspecies of the gray wolf.

These conclusions were published today in the consensus report “Evaluating the Taxonomic Status of the Mexican Gray Wolf and the Red Wolf” by the National Academies of Science.

Joe Travis, Robert O. Lawton Distinguished Professor in the Florida State University Department of Biological Science, served as the research committee’s chair. He said enough prevailing genomic evidence existed to question the taxonomic status of these animals, given both types of wolves had been driven to near extinction in the wild and that questions had been raised about whether the remaining individuals were the product of hybridizations with other species.

The study was commissioned in 2018 by the U.S. Fish and Wildlife Service in order to develop an independent assessment. Travis briefed federal officials on the findings Wednesday.

“The current extant populations of Mexican gray wolves and red wolves are based on captive breeding colonies that were established for each species, and members of which have been released into the wild in North Carolina, so there’s reason to investigate this question, since we’re looking at a population based on a small number of founders,” Travis said.

Concluding the Mexican gray wolf (Canis lupus baileyi ) is a valid subspecies, in fact the most distinctive wolf subspecies in North America, was relatively straightforward, Travis said, referring to the animals’ unique size, coloration, shape and genetics.

“There was no evidence of hybridization with coyotes, no evidence of any past introgression of genes from domestic dogs,” Travis said. “We know the extant wolves are descendants of the historical wolves because they were the last remaining Mexican gray wolves were taken from Mexico and used as breeding stock. You can show the genetic continuity.”

The taxonomic status of red wolves (canis rufus), however, has been a subject of controversy due to intermingling of gray wolf and coyote traits through cross-species mating. Part of the challenge for the group was the relative dearth of a historical, paleontological record for these particular wolves.

Scientifically, there is no doubt that red wolves contain significant genetic material from both gray wolves and coyotes, and that they are more closely related to coyotes than they are to gray wolves. However, the committee’s findings indicate there truly was a historical red wolf.

“The first red wolf specimen dates to 10,000 years ago and was found here in Florida,” Travis said. “If you look at the genes in the managed population in North Carolina, those wolves share these specific red-wolf genes with a previously undiscovered group of red wolves living on Galveston Island, in Texas.”

An additional reason for the controversy surrounding the taxonomic status of these two types of wolves is that while current methods for describing and analyzing genomes are the most sophisticated in history, these methods do not always deliver an unambiguous picture for groups that are evolving rapidly or have some level of mating between species, known as admixture.

Mating and behavioral activity are also important considerations in the committee’s determinations and deliver more insight into reasons for red-wolf hybridization. Wolves mate assertively; if a breeding pair is disrupted, the other animal will seek another mate from within its own species. If one is unavailable, it will mate with a different species.

“Looking into the behavioral data in the context of wolf habitat, the habitat has changed dramatically,” Travis said. “Many places in North Carolina, at the edge of the protected area, the habitat is farmland, which is neither coyote habitat nor wolf habitat. That’s where you see hybrids and why you see them in that location.”

Travis stressed that to do the analysis, it was important to focus on both the genomic and ecological record.

“The study is groundbreaking because it extended beyond a purely genomic study and integrated all available evidence,” he said. “We read all the literature, invited people to come and speak to us, and conducted webinars. And through the generosity of other scientists who shared unpublished manuscripts, we were even able to review unpublished data. We digested and assimilated all of it to write this report.”

In addition to Travis, the committee included geneticist Fred Allendorf, wolf behavioral biologist Diane Boyd, mammalian hybridization and genetics expert Lori Eggert, canid geneticist Diane Genereux, evolutionary genomics expert Michael Lynch, mammalian geneticists Jesús Maldonado and Liliana Ortiz, and computational genomicist Rasmus Nielson.