June 9, 2017 by Ricki Lewis, Phd,
Plos Blogs
Are the red and eastern wolves
separate species, or hybrids with coyotes? And what has that got to do with
climate change? Actually a lot, in illustrating what scientific inquiry is and
what it isn't.
Comparing canid genomes
A report in this week's Science Advances
questions conclusions of a 2016 comparison of genome
sequences from 28 canids. The distinction between "species" and
"hybrid" is of practical importance, because the Endangered Species
Act circa 1973 doesn't recognize hybrids. But DNA information can refine species
designations—or muddy the waters.
At first, genetic marker (SNP)
studies hinted at a mixing and matching of genome segments among coyotes,
wolves, and dogs. Then came full-fledged genome sequencing.
Last year Bridgett M. vonHoldt,
head of Evolutionary Genomics and Ecological Epigenomics at Princeton and
colleagues, scrutinized the 28 full genome sequences for signs of "lack of
unique ancestry." They compared the genomes of 3 domestic dog breeds
(boxer, German shepherd, and Basenji), 6 coyotes, a golden jackal from Kenya,
and various wolves to 7 "reference" genomes from 4 Eurasian gray wolves (to minimize recent
mutations) and 3 coyotes. The conclusion: lots of genes have flowed from
coyotes and gray wolves into the genomes of the animals that became what we
call red and eastern wolves, in different proportions.
A bit of background.
Red wolves were declared
endangered in 1973. A dozen animals, selected by appearance and absence of
coyote traits in their young, were "captively" bred to establish a
population in North Carolina that is now several hundred strong. The 3 red wolf
genomes evaluated in the 2016 study came from NC. Historically the animals are
from the southeastern US.
Gray wolves and coyotes,
according to the 2016 study, are "very close relatives with a recent
common ancestry," although there's about as much genetic variability
between the two species as within each.
Eastern wolves are from the Great
Lakes and the Algonquin Park region of Ontario, moving eastward.
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