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Archive for the ‘wild dogs’ Category

loggerhead sea turtle hatching

Recently, I’ve been using this space to play around with the fuzziness of “species.” Hundreds of species concepts exist, and because different researchers have somewhat different perspectives, you will sometimes get real conflicts about whether something is a species or a mere subspecies.

In canids, we get caught up in species discussions that are about what really amounts to very little genetic variation. For example, red wolves, Eastern wolves, gray wolves, dogs, dingoes and coyotes are all lineages that have only radiated in the past 50,000 or so years.

By contrast Old World and North American red foxes, including the ones allegedly derived by those set out by English colonists in the seventeenth and eighteenth, last shared a common ancestor 400,000 years ago.  This finding means that we probably should regard the red fox of North America as Vulpes fulva.

But 400,000 years of divergence is nothing compared to the 3 million years estimated for the Indo-Pacifica and Atlantic-Mediterranean populations of loggerhead sea turtle. There has been some gene flow between the populations. Matrilines have flipped around South Africa, once 250,000 years ago and an once 12,000 years ago.

So researchers who specialize in wolf-like canids are debating over very small genetic differences and relatively recent divergence times.  Red fox researchers are only just now realizing that there are likely two species in what was once thought to be a Holarctic species. And those specializing in loggerhead sea turtles don’t really care that their species has such a deep genetic difference.  The occasional gene flows between populations are enough for them to recognize only one species of loggerhead sea turtle.

This problem gets more interesting when we start talking about “living fossil species.” Take this article on Futurity.org, which is entitled “Evolution Hasn’t Revamped Alligators in 8 Million Years.” This article discusses the findings of some paleontologists at the University of Florida, who have found 8-million-year-old alligator fossils in North America, and they are remarkably similar to the ones we have today.

One of the researchers is quoted in the article says,”We were surprised to find fossil alligators from this deep in time that actually belong to the living species, rather than an extinct one.”

I would be just a hair more careful in my language. Although one can certainly see that these ancient alligators looked and probably behaved very much like the current species, 8 million years is a long time. I doubt that current alligators and those from that time could even interbreed if they encountered each other today. From a biological species perspective, it makes little sense to call them the same species, but from a paleontological perspective, it makes more sense, simply because paleontology is more interested in morphology and ecology over the entire time a population has existed.

So yes, “species” is a nebulous concept, and that is a good thing.  It makes some legal aspects with conservation difficult, because we have an Endangered Species Act that is about a hard and fast definition of a taxonomic entity.  In reality, the whole nebulous side makes for interesting levels of inquiry. If the Neo-Darwinian synthesis correctly describes the origin of biodiversity, then we would expect these discussions and debates to be commonplace.

They certainly are quite common in taxonomy and systematics. They probably always will be. Part of what defines a species are the biases of the classifier, which can often be contradictory.

For example, I have no problem with the new taxonomy of wildcats that posits the European wildcat into a different species than the Near Eastern/North African species. However, I disagree with the position of the domestic cat, which derives fro the Near Eastern/North African species, as its own unique species.

That bias may come from the simple fact that I am more familiar with domestic dog taxonomy, and I have come to accept that domestic dogs are best classified as a divergent form of gray wolf. If the domestic cat derived from its wild ancestor much more recently than the dog derived from its wild ancestor, why would it make any sense to classify the domestic cat as its own species?

So in zoology, we have all these different perspectives on how to classify species. Specialists in sea turtles are able to tolerate a genetically quite divergent species, while experts in wolf-like canids will debate over much more recently divergent lineages. These researchers really don’t talk to each about their ideas.  Indeed, the only time loggerhead sea turtle researchers worry about what specialists on the wolf-like canid side are doing is when they need to figure out how to stop coyotes from destroying the turtles’ nests. But they don’t need to know the complexity of the systematics to find an answer.

However, it is amazing how different specialists come to tolerate variation within one species. That nebulous nature of the various species concepts makes for some interesting variations on what specialists accept as normal.

Specialists often have very different ideas in mind, depending upon what they are used to, and I find it beautiful, even if it a bit confusing at times.

 

 

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sicilian wolf

Italian wolf (Canis lupus italicus) at left and the newly described Sicilian wolf (Canis lupus cristaldi).

The Mediterranean islands of Sicily, Sardinia, and Corsica are quite interesting from a natural history perspective.  Insular endemics have occurred on these islands throughout their history, and over the years, one species has captured my imagination, the so-called Sardinian dhole, which was found on both Sardinia and Corsica.  I’ve been trying to trace down exactly what this species was for quite some time, but so much is contentious about this animal that I’ve left it alone, still awaiting that paper that will elucidate it in all its glory

But recently, I’ve become aware of something more tangible: an insular dwarf form of gray wolf that was found in the island of Sicily.  This wolf existed well into the twentieth century, and we have many specimens of them from which we can make measurements and take DNA samples.

In 2018, a paper was published that described the Sicilian wolf’s morphology and contained some initial mitochondrial DNA analysis. The wolf is described as standing on average 21 inches (54.6 cm) at the shoulder, which is about the same height as a coyote.

sicilian wolf taxidermy

These small wolves ranged throughout Sicily and were persecuted as lamb killers. The last documented taking of a wolf on Sicily was in 1924, but reports of hunters killing wolves persisted until 1938.  Sightings were reported from 1960s into the 1970s, but since then, the reports of the Sicilian wolf have largely gone dry. The subspecies is almost certainly extinct.

Analysis of the mitochondrial DNA from two museum specimens revealed that these wolves had a slightly different signature from the mainland Italian wolf. The authors attribute to the Sicilian wolf’s evolution in isolation, which likely started between 20,000 and 21,500 years ago, when the last known land bridge connecting Sicily and mainland Italy was around.

In about 20,000 years or so, insular dwarfism selection pressures produced a small wolf on Sicily in much the same way we might understand how an earlier Pleistocene radiation of wolves into North America could have created another form of small gray wolf that we call coyotes.

The coyote didn’t evolve its smaller size to fit the ecological needs of living on an island. It had to evolve its smaller size to fit a more generalist niche than try to compete as an apex predator on a continent already dominated by dire wolves.

So we have this sort of evolution of coyote-like wolves in parallel in the Old World, which is entirely within our understanding of the gray wolf as a phenotypically and behaviorally plastic species that has had great success adapting to new ecosystems throughout Eurasia and North America.

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red wolf

So I’ve been sent this story a couple of times: apparently, a genetic analysis of Galveston Island coyotes found a relationship between these coyotes and what are called red wolves that are part of the US Fish and Wildlife Service’s endangered species recovery program.

I found it interesting that Bridgett vonHoldt was part of the study that found this genetic link between Galveston Island coyotes and red wolves. VonHoldt is one of the leading canid molecular geneticists who was part of a team of researchers that have found that the red wolf is of hybrid origin. She was also an author of the paper that shows the biggest problem that the red wolf has in claiming species status.

This problem is that it really doesn’t matter whether red wolves are hybrids or not. The question is whether they are hybrids between two entities that are best described as distinct species or not.

A comparisons of full genomes of gray wolves, Eastern wolves, red wolves, and coyotes revealed that Eastern wolves and red wolves are hybrids between coyotes and gray wolves. This finding has been revealed in three papers, one in 2011, one in 2016, and one in 2018. This hybrid discussion is tiresome, though, because we can get into a sea-lioning contest about how there might very well be a hidden unique red wolf species hidden somewhere in the coyote.

This paper would appear to have found such a thing, but it needs to be understood within the full context of the literature.

Yes, the genome-wide and full genome comparisons reveal a hybrid origin of red and Eastern wolves, but the problem that no one seems to be willing to deal with is how recently gray wolves and coyotes split.

When it seemed like gray wolves and coyotes had a common ancestor 800,000 to a million years ago, debates about hybrid origin made some sense. But in the 2016 study, the authors did some comparisons of gray wolf and coyote DNA to see if they could find when the two forms of canid split. The most statistically valid date for that common ancestor was alive around 50,000 years ago:

If we assume a generation time of 3 years, and an effective population size of 45,000 (24, 25), then this corresponds to a divergence time of 50.8 to 52.1 thousand years ago (ka), roughly the same as previous estimates of the divergence time of extant gray wolves (26–28). Thus, the amount of genetic differentiation between gray wolves and coyotes is low and not much greater than the amount of differentiation within each species (for example, Eurasian versus North American gray wolf, FST = 0.099; Table 2 and fig. S1).  This result contradicts molecular clock calculations based on short mitochondrial control region sequences, which were calibrated using a 1-Ma (million years ago) divergence time between gray wolves and coyotes (10). Despite body size and other phenotypic differences between the two species [for example, (1)] and a long history of coyote- and wolf-like forms in North America (1, 29), the genomic data suggest that modern coyotes and gray wolves are very close relatives with a recent common ancestry. (Italics mine).

This paper shows that what we call a coyote could best be described as a form of gray wolf, a smaller and more jackal-like form of gray wolf to be sure but a gray wolf nonetheless. I don’t know why the authors didn’t make this suggestion, because a similar way of thinking clearly puts pugs and Newfoundlands in the gray wolf species as well. This classification is controversial, but it’s not that controversial if you understand systematics based upon clade-based thinking.

So what the researchers found Galveston Island is a population of coyotes that share some genetics with the red wolf. The population that founded the red wolf population that receives conservation attention came from the East Texas and Louisiana mainland, and if this population is isolated, then you can see how this unique population could have retain its genetics as more coyotes spread through the mainland on their way East.

Even if we were to find that there were once large wolves in Prehistoric North America that had coyote-like mitochondrial DNA, we would still have that problem of the recent coyote origins. The only way that problem might be solved is if these large wolves are significantly older than the date suggested from the gray wolf-coyote split. Because we know that anatomically modern gray wolves already existed in Eurasia well before the coyote-gray wolf split, one would expect to find large wolves with coyote-like DNA in North America. We also should expect to find wolves with coyote-like DNA in the Old World as well.

The real debate should be about the validity of Canis latrans as a species. The problem with going down this road is more political than scientific. Coyotes are the most successful relatively large canid in North America. They are found in 49 states, and the only reason they aren’t in Hawaii is they can’t swim that wall.  They are working their way down through Panama, and I would not be surprised if I read some morning that they had crossed the swamps of Darien into Colombia.  Coyotes receive almost no protections anywhere in their range, while wolves generally are protected via the ESA where their populations have been reduced or extirpated.

But we don’t regard domestic dogs as a species either. One can easily see them as a divergent form of gray wolf without losing perspective that there really ecological distinction between a domestic animal and a top-level predator. We are currently grappling with the evidence that dog genes are introgressed heavily into Eurasian wolf populations, but almost exactly the same thing has been observed with North American wolves and coyotes. Even the wolves of Alaska and Yellowstone have coyote ancestry.  

So one should have a bit of skepticism about what was actually discovered on Galveston Island.  At the very least, we should be very careful about thinking of gray wolves, dogs, and coyotes as hard and fast entities and that all three continue to exchange genes across their respective ranges.

We do have a species problem, a species problem that would make sense only if Darwininan precepts are true. With this clade in Canidae, we have also have the Ethiopian wolf, the African golden wolf, and the Eurasian golden jackal that are capable of exchanging genes with each other and with dogs and Holarctic gray wolves. Indeed, the African golden wolf is derived from either a gray wolf or a gray wolf ancestor interbreeding with the ancestral Ethiopian wolf, which was probably much more widespread in the past. 

I don’t have as much of problem thinking of coyotes as a form a gray wolf, probably because I’ve long since accepted that domestic dogs are also a form of gray wolf, but thinking in this way is disruptive to our concept of hard and fast species. However, we should never think that such thing as a hard and fast species exists in the first place. Evolution is fundamentally about change, but it’s also about fuzziness and questions that harry our concepts of essentialism.  

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Coyotes, nature’s sighthounds

Built a lot like a lurcher.

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Great Lakes gray wolf on Wisconsin’s Stockton Island.

An extensive camera trap survey of the Apostle Islands in Lake Superior has revealed a great diversity of carnivorans, including gray wolves and American martens. These islands, located just off Wisconsin’s Bayfield Peninsula, are among the few places left in the Eastern and Midwestern US that still retain an intact predator guild, and because all but one of the islands is protected as a national lakeshore, these islands will be protected from most exploitative development.

I love living in a country that still has room for wolves and wild places. Our natural heritage is every bit as important to us as a nation as our constitution and rule of law, and it should be protected with the same ferocity that we use to protect our republicanism.

Also of importance is the Great Lakes wolf in the trail camera capture that was part of the survey. This wolf looks to be one of wolves with some amount of coyote introgression. Great Lakes wolves can have quite a high amount of coyote ancestry, and the earliest estimated introgression of coyote genes into gray wolves that has been documented is from these Great Lakes wolves. This introgression happened as early as 963 years ago.

Coyotes and gray wolves are found on the islands now, and one wonders if they still occasionally interbreed. The Great Lakes are also the region that experienced the beginnings of the hybrid swarm we call the Eastern coyotes.

So these islands could be a new Isle Royale from which to study the new and evolving wolf and coyote of North America.

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Clive enjoyed his snowy walk this morning.

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Photo by Alexander Badyaev

It’s no secret that I have a bit of infatuation the canids in the genus Urocyon. Not only are they considered the most basal form of extant canid, it is very likely that there are multiple cryptic species in the genus that need more molecular and morphological investigations to ascertain.

These canids are unique among North American dogs in that they are great tree climbers. Indeed, they are the most arboreal of all dogs. While the raccoon dogs of the Old World certainly do climb with their long hooked claws, the gray foxes take to the trees as readily as cats do.

A few years ago, I came across these images of some Southwestern gray foxes climbing in trees that were adorned with skeletons. I initially thought they had been placed in these trees to attract the foxes to the trail camera, and I pretty much ignored them.

But today, I was snooping around the web in search of the latest stories on gray foxes, and I came across the full story of these images. It turns out that the gray foxes of the Sonoran Desert often cache prey and scavenged food items in trees to keep them safe from coyotes. They use these “skeleton trees” as places where the whole family group gets together to groom and bond and rearrange their caches.

The most unusual photo from the series shows a gray fox standing on a branch where it has placed a dead collared peccary (javelina) “piglet.” The adults of this species are so much larger and so much more aggressive than any gray fox, and I cannot help but wonder how the gray fox managed to catch such a trophy. It had to have taken some guts if the fox caught it on the run, but the researcher who got these photos claims that the foxes do trail peccaries in hopes of snatching a little one.

Lots of research goes into wolves and coyotes. They are the charismatic canids of North America, and both North American and Old World red foxes have also been extensively studied.

But gray foxes don’t get that same billing, and that is pretty sad. They are not like the short-eared dog of South America, where they intentionally live as far from human settlements as possible and are quite difficult to study. Gray foxes are pretty common in North America, if you live south of Canada and outside of the Northern Rockies and the Northern Great Plains of the United States.

I think the name has something to do with it. The name “gray fox” has a connotation with something drab and bland, while “red fox” has a spicier feel.

One implication of the recent finding of the potential existence of two species of gray fox on the North America mainland is that the proposed Western species might derive from an Irvingintonian Urocyon that is not ancestral to the proposed Eastern species.

This analysis was derived from a limited mitochondrial DNA analysis and should be taken with a grain of salt, but it seems likely that at least two species really do exist on this continent. More work from the full genome needs to be performed, and my guess is this research is currently being performed. The article might be out in peer-review right now, and one day, we’ll know for sure.

But there is something mysterious about these little canids. They are move like little cat-dogs, and in the Southwest, at least, they are little dog-leopards, caching their prey in trees where the coyotes can’t go.

The more we know about these lesser dogs, the more they intrigue me. Indeed, the whole lesser parts of Carnivora have me a bit enthralled. The tiger is largely known, as is the wolf, but the mysteries lie with the Eastern spotted skunk in the High Alleghenies of West Virginia, with the long-tailed weasels of canyon lands of New Mexico, and with the bat-eared foxes of the Kalahari.

So now, we must consider the meek and the mild and drab. We must now come to know them, to let their mysteries be revealed in all their glory. We will be shocked, I’m sure

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