The Enigmatic Small Wolf Species of the Early-Mid Pleistocene of North America

There were at least 5 species of wolf-sized canids living in North America from about ~1.8 million years BP-~300,000 years BP.  Edward’s wolf (Canis edwardii) was a medium-sized canid, averaging about 75 pounds, that apparently occurred from coast to coast.  It’s the same species formerly known as Canis priscolatrans, and it was an evolutionary dead end–its extinction occurred about 300,000 years ago.  Armbruster’s wolf (Canis armbrusteri) co-occurred with Edward’s wolf but was a larger species, weighing on average 125 pounds.  Armbruster’s wolf is thought to be the evolutionary ancestor of the famous dire wolf (Canis dirus) which became extinct about 11,000 years ago.  Troxell’s dog (Protocyon texanus) was related to African hunting dogs.  Fossil evidence of this species has been found in Texas, the Yukon, and Alaska; and it probably had a wider range than the fossil record indicates.  Perhaps it lived in low numbers in geographic regions where processes of preservation were rare. The timber wolf (Canis lupus) was apparently confined to Alaska and Eurasia during the mid-Pleistocene and didn’t colonize North America until the late Pleistocene.  Finally, a mystery species nearly identical to the present day coyote (Canis latrans) left fossil evidence at sites in Nebraska, Colorado, California, Arkansas, Pennsylvania, Maryland, and West Virginia.  Some of the fossils at these sites are estimated to be 1 million years old.  Paleontologists identified these specimens as Canis latrans, though they cautiously also referred to them as coyote-like.  However, a recent study of wolf, coyote, and dog genetics determined the coyote is a recently evolved species no older than 50,000 years when it first diverged from timber wolves.  This result suggests the mid-Pleistocene species identified as Canis latrans may be an extinct mystery species.

In addition to the fossil record scientists can use a molecular clock to determine when 2 or more species diverged from a common ancestor.  A species has a fixed mutation rate, and scientists add up generations of mutational changes to determine the time of divergence from its closest related species.  (This is a vastly oversimplified explanation but will suffice for the purpose of this blog article.)  There are problems with using molecular clocks.  Different species have different rates of mutation, and the mutation rate can change over time.  Scientists try to calibrate the molecular clock with the fossil record by using various statistical methods.  An early study of wolf and coyote genetics determined the 2 species diverged about 1 million years ago, and this result is consistent with the fossil record, but the results of the newer study mentioned above totally contradict the fossil evidence.  There are 2 explanations for this discrepancy.  a) The new study is wrong.  Maybe the scientists used too many assumptions and dodgy statistics and just came up with the wrong number.  or b) The new study is right, and the mid-Pleistocene species identified as Canis latrans was an evolutionary dead end that went extinct.  The similarity between this mystery species and Canis latrans is just a remarkable example of convergent evolution. c) The new study is right and is not inconsistent with the fossil record.  Perhaps the common ancestor of the coyote and timber wolf was coyote-like.  Ice Age glaciers caused the divergence.  Populations north of the Cordilleran ice sheet evolved into timber wolves but populations south of it remained coyote-like.

Below are images of mid-Pleistocene  skull and jaw specimens identified as Canis latrans along with the skull and jaw of a present day coyote.  I can’t tell the difference, so I favor explanation a.  Even in a case of convergent evolution, there would have to be some notable anatomical differences between 2 different species.

Genetic evidence from 1 study suggests coyotes diverged from gray wolves about 50,000 years ago.  However, this skull, assigned to Canis latrans (coyote) from Maryland dates to >300,000 years ago.  Is the genetic evidence incorrect or was there a species then so similar to modern coyotes it deceived paleontologists? Image from the below referenced paper by Tedford et. al.

Present day skulls of Canis latrans.

Some zoologists think coyotes and dogs should now be classified as subspecies of timber wolf based on the data from the newer genetics study.  I don’t agree.  The behavioral characteristics of wolves, dogs, and coyotes are too dissimilar; and they don’t normally interbreed in natural conditions.  Humans can easily eradicate wolves from a region, but they can not eliminate coyotes because the latter are so much better adapted for living close to people.  Wolves and coyotes can survive in the wilderness, but they make terrible pets.  Most dogs make excellent companions for people but can’t survive in the wild.  In my opinion wolves, coyotes, and dogs are closely related but definitely different species.

References:

Tedford, Richard; X. Wang, and B. Taylor

“Phylogenetic Systematics of the North American Fossil Caninae”

Bulletin of the American Museum of Natural History  2009

Von Holdt, Bridgett; et. al.

“Whole Genome Sequence Analysis Shows that Two Endemic Species of North American Wolf are Admixtures of Coyote and Gray Wolf”

Science Advances (27) July 2016

Wilson, Paul; et. al.

“DNA Profile of Eastern Canadian Wolf and Red Wolf Provide Evidence for a Common Evolutionary History Independent of the Gray Wolf”

Canadian Journal of Zoology 2000

 

 

 

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The Truth About the Red Wolf’s Status as a Species

There are a lot of hostile jerks on the internet who are quick to insult the intelligence of people they disagree with. Not long ago, I encountered one of these shmucks.  Scottie Westfall writes the Retrieverman blog which is an interesting one focusing on dog breeding, evolution, and genetics.  He’s convinced recent genetics studies support his long held belief that the red wolf (Canis rufus) is nothing more than a hybrid between the gray wolf (Canis lupus) and the coyote (Canis latrans).  I commented on his blog, suggesting how the natural history of this hybridization could have occurred beginning in the Pleistocene.  My comment was consistent with the findings of the study he cited.  I wasn’t disagreeing with his premise.

 A Shmuck on the internet.

His response to my comment revealed blind hostility.  He wrote that my “inability to understand the study and my parrotting of data it falsified was telling.”  This would be a cleverly worded retort, if I had been in conflict with his opinion.  But I wasn’t.  It was obvious he didn’t understand what I wrote because I wasn’t even disagreeing with his conclusion.  And his response implied that I was some how evil or an idiot simply because we supposedly disagreed about some obscure scientific controversy.  On this same response thread he’s carrying on a long debate (92 responses and counting) with an ardent anti-hunter in which his tactic is to call her an “idiot.”  What’s that say about his mentality and personality?

Now, I’ve had time to read the literature in depth, and I’ve discovered the genetic studies are contradictory.  Evolution is seldom black and white.  Usually, there is quite a bit of gray area, and the status of the red wolf as a species is certainly an example of the uncertainty involved in determining when speciation has occurred.  Scottie Westfall’s blog gives only one side of the issue–the genetic studies that support his opinion.  I commented on his blog with a link to a study that contradicted the genetic studies he touts as conclusively supporting his position, but he removed my comment and apparently he’s decided to block all of my comments from now on.  Because his blog tops google searches, I feel it’s necessary to offer both sides of this issue, so those researching this controversy can gain a better unbiased understanding.

Red Wolf (Canis rufus? Canis lycaon? Canis latrans x Canis lupus? Canis rufus x Canis latrans? Canis lupus rufus?)

This 80 pound canine was recently shot inside this hog trap somewhere in Georgia.  It’s black and had a white spot on its breast.  Another trailcam photo posted at the Georgia Outdoor News forum also photographed a black coyote with a white spot on its breast.  Early colonists and explorers in the southeast noted that black wolves with white spots on their breasts were the common color variation of wolves in Georgia and Florida.  I’ve also seen large reddish colored coyotes in south Richmond County Georgia.  Supposedly, wolves were extirpated from Georgia and Florida by 1917.  Did a population survive?  Is it breeding with the recent influx of western coyotes or was the southeastern wolf simply a big subspecies of coyote?  DNA tests are contradictory.

All scientists agree that the remaining population of red wolves, now confined to the Alligator Wildlife Refuge in North Carolina, have at least some coyote blood.  The final population of red wolves captured along the Lousiana/ Texas border had been reduced to such low numbers that they’d been breeding with the more abundant coyotes.  Scientists chose those individuals with the physical characteristics most consistent with those of the red wolf and successfully bred them in captivity before releasing them in the North Carolina wildlife refuge which then was far away from the expanding coyote population but now suffers a coyote invasion.  Biologists are attempting to trap and remove coyotes to prevent them from again breeding with red wolves, but I doubt they’ll be successful.

About 20 years ago, R.K. Wayne of UCLA noticed an absence of genetic markers in red wolves distinct from those of coyote or gray wolf.  He proposed that the red wolf was simply a coyote/gray wolf hybrid.  A few years later, he examined DNA from 6 skins of red wolves killed in Arkansas circa 1900, and the evidence supported his proposal.  A few other studies supported his contention, but other scientists were skeptical.  They were suspicious of Dr. Wayne’s choice of specimens.  They originated from Arkansas which bordered the historical range of the gray wolf and the red wolf.  The specimens may in fact be from gray wolves, not red wolves.

In 2000 Dr. Paul Wilson, a Canadian scientist, led a study of eastern Canadian wolf and red wolf DNA.  He found none of the eastern Canadian wolf or red wolf DNA from specimens prior to the 1960’s contained gray wolf mtDNA sequences.  Moreover, there was a high degree of genetic affinity between eastern Canadian wolf (Canis lycaon) and red wolf mtDNA.  He considered them the same species.  In both wolves he found mtDNA control sequences more closely related to coyotes that are not found in gray wolves.  However, both eastern wolves had specific unique haplotypes not found in western coyotes.  So his study did find specific genetic markers unique to red wolves that were not found in gray wolves or coyotes–something Dr. Wayne didn’t find in his study proposing that red wolves were coyote/gray wolf hybrids.  Below is his proposed evolutionary tree which is consistent with the fossil record.

Dr. Wilson found a genetic divergence between gray wolves and eastern wolves of 8% which he calculated to mean they diverged from a common ancestor 1-2 million years ago.  The genetic divergence between coyotes and eastern wolves is only 1-2% which he calculated to mean they diverged from a common ancestor 150,000-300,000 years ago.  Coyotes have recently (within the last 100 years) come into contact with eastern wolves and have hybridized.

Last year, scientists led by Bridgett Von Holdt used existing genetic data to create a genome wide analysis of worldwide canine DNA.  The findings in this study directly contradict the findings in Dr. Wilson’s study, though it should be noted this study used the same contested samples of red wolf specimens that Dr. Wayne used.  Dr. Von Holdt found no close affinity between eastern Canadian wolves and red wolves.  They determined the current population of red wolves were 75%-80% coyote with the balance being gray wolf.

So which study is correct?  Who knows?  I would like to see a study of DNA from red wolf specimens originating from 17th or 18th century Florida, Georgia, Alabama, and Tennessee.  Evidence from such a study might resolve the controversy.  I’m not sure a study such as I propose can be conducted.  There may just be a shortage of readily available museum specimens.  But I know of one.  I recall a red wolf specimen with fur was discovered in Fern Cave, Alabama in 1970 along with much older remains of the giant short-faced bear (Arctodus simus).  I don’t know who possesses this specimen but it should be genetically analyzed.

I believe red wolves evolved from coyotes following the extinction of dire wolves.  Coyotes were present in the Pleistocene southeast but eventually became absent.  I formerly thought red wolves drove coyotes out of the region, but now I think eastern coyotes grew bigger to exploit a deer-hunting niche left vacant when dire wolves became extinct.  Whether or not they’re a distinct species, a large subspecies of coyote, or a coyote/gray wolf hybrid is debatable?

References:

Wayne, R.K.

“Molecular Evolution of the Dog Family”

Trends in Genetics 1993

Wilson, Paul; et. al.

“DNA Profiles of Eastern Canadian Wolf and Red Wolf Provide Evidence for a Common Evolutionary History Independent of the Gray Wolf”

Canadian Journal of Zoology 78 2000

Von Holdt, Bridgett; et. al.

“A Genome Wide Perspective on the Evolutionary History of Engimatic Wolf-like Canids”

Genome Research 2011

Pleistocene Fossil Canid Ratios Recorded in the University of Florida Database

The abundance of Pleistocene fossil sites in Florida has allowed the university in Gainesville to become a center of information for other scientists.  Scientists excavating new fossil sites use existing fossils at the University of Florida Museum of Natural History to help identify the new specimens they pull from the earth.  It’s not always easy to differentiate closely related species–the subject of this blog entry, the canids, are notoriously difficult to distinguish.  Vertebrate zoologists and paleontologists measure and describe every part of every bone and tooth when examining new specimens.  They publish this information in scientific journals and accumulate knowledge of the size limits and shape variations of a particular species’ anatomy.  If a newly discovered fossil tooth for example doesn’t fit any known pattern of shape or size, than scientists suspect they may have discovered a new species.  The more data scientists have, the better able they are to identify new species and spot evolutionary trends over time within a species.

Fossil collecting is popular in Florida, thanks to all the sinkhole lakes and caves with basal chemistry in the soil that preserves bones.  Amateur fossil collectors have many more fossils in their collections than the University of Florida’s Natural History Museum..  Many are for sale as well.  It would be a great benefit to science, if collectors made arrangements to donate their collections to the museum upon their deaths.  Many valuable specimens have been lost when their owners die and family members, not interested in the subject, lose track of where they put the old bones.

My little study is limited to canid fossils listed on the University of Florida database and leaves out the great many more in the hands of amateur fossil collectors.  I also limited this survey to the Rancholabrean Land Mammal Age (300,000 BP-11,000 BP), leaving out Armbruster’s wolf which dominated the middle Pleistocene before being replaced by dire wolves.  Nevertheless, I think there’s enough information to suggest relative canid species abundance during the late Pleistocene.  Keep in mind, I was counting on a computer screen while scrolling down, so my numbers may be off slightly.

Listed on the Florida Museum of Natural History’s database, I counted 64 dire wolf (Canis dirus) specimens, 34 coyote (Canis latrans) specimens, 1 red wolf (Canis niger) specimen, 9 domestic dog (Canis familiaris) specimens, 0 dhole (Cuon alpinus) specimens, and 55 gray fox (Urocyon cineorgenteus) specimens.

The fossil record strongly suggests that from 300,000 BP to about 11,000 BP dire wolves were by far the most common large canid being about twice as abundant as coyotes.  Red wolves were rare but present.  Gray foxes were just as common during the Pleistocene as they are today.  These neat little foxes have the ability to climb trees, a skill that saves them from their larger relatives.  There is no evidence of dholes but as I wrote in a previous blog entry http://markgelbart.wordpress.com/2011/06/01/did-the-dhole-cuon-alpinus-range-into-southeastern-north-america-during-the-pleistocene/ , I suspect they may have periodically colonized parts of the southeast but in numbers too low to leave fossil evidence.

Dire wolves were the dominant large canid in the southeast (and all across North America south of the Ice Sheets) during the late Pleistocene.

Coyotes probably occupied a niche similar to African jackals.

Gray foxes thrived in areas where they had access to trees and could escape larger predators.

The presence of domesticated dogs in the Pleistocene fossil record puzzled and surprised me.  I almost didn’t even do a database search for Canis familiaris and only did so as an afterthought.  Most anthropologists don’t think humans domesticated dogs until after the Pleistocene about 10,000 years ago, but the fossil evidence contradicts this.  In fact scientists recently discovered the skull of a domesticated dog in a Siberian cave that dates to 33,000 BP.  They determined  this particular domesticated dog was not the ancestor of the lineage that led to today’s dogs but instead its descendents died out.  It’s probable that there were many early lineages of domesticated dogs that ceased to exist for various reasons.  Perhaps that group of people died out or stopped keeping dogs.  The popular idea that people domesticated dogs by kidnapping and raising wolf pups is a misconception.  Scientists think it’s the other way around–dogs adopted us.  Dogs are descended from the wolves which had the least flight response.  Wolves that hung closely around human campsites for access to leftovers gave birth to pups with floppy ears, multi-colored coats, and other dog traits that differentiate them from other wolves.  The gene for tameness shares a pathway with the gene for these physical characteristics.  So it’s likely that dogs adopted people in many different geographic locations wherever wolves (Canis lupus) began occupying areas adjacent to human campsites.  Obviously, dogs either followed or were brought to Florida by the Paleo-Indians.

The authors of a chapter in the book The First Floridians and the Last Mastodons suggest that all the coyote fossils found in Florida are actually domesticated dog fossils, but they only knew of a handful of coyote fossils.  Apparently, they didn’t know 34 specimens had been found.  I doubt scientists made that many misidentifications.

Dire wolves succeeded in becoming one of the dominant predators in the environments of southeastern North America where they found a wealth of prey roaming the open woodlands and savannahs.  Everything from bison and horses to deer and rabbits sustained them, and a mammoth or mastodon that died of natural causes provided a feast.  Coyotes successfully co-existed with dire wolves by scavenging large predator kills and by hunting rodents.  Red wolves must have been restricted to islands and perhaps deeply wooded swamps where they could survive on deer and small game.  Their niche must have been areas with lower densities of prey as opposed to grasslands that hosted large herds of ungulates.  Following the extinction of the megafauna and dire wolves, forests replaced grasslands and red wolves increased in number and drove coyotes completely out of the south.  But after European settlers wiped out the red wolves, coyotes returned.

References:

Ovodov, Nikolai, et. al.

“A 33,000 Year Old Incipient Dog from the Altai Mountains of Siberia: Evidence of the Earliest Domestication Disrupted by the Last Glacial Maximum”

Plos One 6 (7) 2011

http://www.flmnh.ufl.edu/databases/vp/intro.htm

The Dunwoody Nature Center

I attended my nephew’s bar mitzvah in Dunwoody, Georgia last weekend.  Dunwoody consists of dozens of subdivisions and plenty of shopping centers and absolutely no rural farmland.  I didn’t hold out much hope for a nice nature walk here–the traffic is terrible.  But at least the developers left a lot of trees standing.  I decided to walk from my sister’s house to a little park known as the Dunwoody Nature Center and I discovered a surprising gem.

This white oak was about 4 feet in diameter.  White oak is a common tree in Dunwoody.

From the composition of the trees left standing most of Dunwoody must have once hosted a pretty nice dry upland forest.  Too bad developers converted it into a crowded suburb.  Today, white oaks, black oaks, southern red oaks, shortleaf pines, and loblolly pines are the dominant trees.  The Dunwoody Nature Center slopes sharply down toward Wildcat Creek, the name of which is a relic to its former status as a wilderness.  The woods here are dominated by beech, white oak, sweetgum, river birch, and loblolly pine.  I was stunned to see a woodlot of mostly beech trees in central Georgia.

A mature beech tree growing on the edge of a rocky creek.  It’s surrounded by many immature beech saplings.

Fossil pollen studies show beech was a common tree in the south during the end of the Ice Age when the Laurentide glacier began melting and releasing more moisture in the atmosphere creating a climate that was still cool but more rainy than it was during the height of the Ice Age.  The presence of abundant beech in the fossil record is indirect evidence of massive flocks of passenger pigeons.  Passenger pigeons fed on acorns–in some places completely eliminating the oak seed crop…and the beech’s competition.  Although beech trees produce an edible nut, they can also spread from roots and could survive their seed being consumed by passenger pigeon flocks.  Since the passenger pigeon’s demise, oak forests have been replacing beech forests in many areas.  So I was delighted to see this remnant beech forest in central Georgia.

Wildcat Creek flows through a granite outcropping.  Here is a miniature waterfall.

Two little league baseball fields take up about half the space of the park.  The park is heavily used by dog and toddler walkers.  It’s popularity shows that the planning commission in charge of developing Dunwoody should have arranged for the purchase of more land for more parks.