Species, Speciation, Coyotes and Wolves. Part 2 of 2.

Now back to Coyotes and Wolves. Evolutionary biologists measure statistical differences between closely related populations with the “Fixation Index” (FST). It is a measure of population differentiation due to genetic structure. FST values range from 0.0 to 1.0. Modern genomic sequencing of DNA allows very precise examination of DNA differences between organisms. FST also includes a measure of “variation” so FST values can be compared statistically. When FST is larger than 0.35 populations are normally characterized as different species. 

The three extant genus Canis species in North America are all genetically very similar. For example, based on whole-genome sequence data, the pairwise FST value between gray wolves and coyotes is 0.153, between gray wolves and red wolves is 0.177, and between coyotes and red wolves is 0.108 (vonHoldt et al., 2016). All well below the 0.35 threshold!

Reference

About Red Wolves. Red wolves once ranged from Texas to Pennsylvania (centered in the southeastern U.S.) but today are found only in eastern North Carolina. Most are captive bred with less than two dozen in the wild. While there are those who would like to consider the red wolf a distinct species (e.g., Canis rufus) all the molecular evidence points to the fact that Coyote genes have intermixed with gray wolf genes. It is believed that this probably happened as wolves were exterminated in the east and Wolf numbers were low forcing some wolves to mate with coyotes. Even if Red Wolves are really just a sub-species of Gray Wolf they still can be protected under the Endangered Species Act. 

The authority on naming mammals is “Mammal Species Of The World” 2005. An on-line version is hosted by Bucknell University.

The red Wolf is listed as a sub-species of Canis lupus (as is the Mexican wolf which also has coyote genes “admixed”). On the other hand, a study was commissioned in 2018 by the U.S. Fish and Wildlife Service to develop an independent assessment of the status of the Red Wolf. That study suggested the Red Wolf deserves to be named its own species.

https://artsandsciences.fsu.edu/article/red-wolves-mexican-gray-wolves-are-valid-taxonomic-species-researchers-say

So as far as coyotes and wolves are concerned the DNA evidence clearly shows that while they might be classified as two distinct species they really are one species headed toward two species. Behaviorally speaking they seem quite different, perhaps worthy of distinct species names. They are stars in a motion picture measured in many more hours than we are used to; measured not in hours, but in millennia. 

Addendum: Coyotes are poised to expand their range to a new continent. The North American canine native has now reached the Darién Gap – a dense wilderness on the border of Colombia and Panama, at the very doorstep of South America. If the coyote succeeds, it would be a new chapter in an amazing evolutionary story that’s played out over the past half century. What could block their making their way to South America? Jaguars in the forests and the Panama Canal. I think they will make it.

Next Post: Dingos and African Painted Dogs