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Posts Tagged ‘Vulpes vulpes fulva’

A red fox vixen in the Mid-Atlantic part of the USA. Photo by Kris Diaz.

A red fox vixen in the Mid-Atlantic part of the USA. Photo by Kris Diaz.

Red foxes are currently the most widespread wild canid.

This is the same sort of fox that can be found in Egypt, England, and Virginia, and it has been introduced to Australia, where it has become a virulent invasive species, taking out scores and scores of endemic native wildlife.

For many years there was a debate about how to classify the red fox in North America. Unlike Australia, where there is no real case for calling it native wildlife, North America’s red fox population has been a bit controversial.

When the tobacco colonies along the Chesapeake created America’s first landed gentry, there was a move to import well-bred foxhounds for sporting purposes. At that time and in that part of the continent, there were no native red fox populations, so there were accounts English red foxes being introduced to the Virginia Tidewater and the Maryland plantations for sporting purposes.  Red foxes were found in northern New England at the time, so I’ve often wondered why they didn’t just get their foxes from those colonies.

For a very long time, it was just assumed that red foxes living south of New York State were derived from English foxes that were brought over in the seventeenth and eighteenth centuries.

After all, the Australian red foxes were definitely derived from introduced individuals, so it would make sense that there could be an introduced population in the Eastern US.

However, red foxes are found over much of the continental US and Canada, and there are Pleistocene records of red foxes in Virginia.

So red foxes definitely are native to this continent, but the question is whether those in the Eastern US are derived from native populations or from those English imports.

In the early twentieth century, virtually all red foxes in North America were classified as Vulpes fulva, rather than Vulpes vulpes.

But as time progressed, all North American red foxes became classified as Vulpes vulpes, and the Eastern and Midwestern population of red fox became Vulpes vulpes fulva.

Then two papers came out that examined the DNA of red foxes across the continent and in Europe.

In 2012, Stratham et al.  found that their mtDNA of Southeastern and Mid-Atlantic red foxes was very similar to those in Eastern Canada and the Northeastern US, meaning those populations were indigenous North American foxes. They descended from foxes that came into that part of the continent during in the nineteenth century in much the same way coyotes invaded the East in the twentieth century.

Then, in another Stratham et al (2014) paper, it was revealed the Old World and New World red foxes have been reproductively isolated for 400,000 years. This paper also looked at the y-chromosomes and nuclear DNA of 1,000 red foxes from around the world, and it strongly suggests that there are actually two species of red fox. There was some evidence of Eurasian red foxes entering into the Alaskan red fox population 50,000 years ago, but other than that, these two animals might as well be separate species.

Now, I’m a little hesitant to consider that red foxes should be split in two in this fashion, but keep in mind, that in North America, there are two species of Urocyon fox, the mainland gray fox and the island fox. But analysis of mtDNA from both types of Urocyon revealed that the island population only split from the mainland species somewhere between 7,100 and 9,200 years ago.

The lower estimate of that split is at least half the time that dogs and wolves have been split.

And it’s nowhere near the time in which New World and Old World red foxes have diverged.

If we are so willing to have two species of Urocyon, then there is way that we can have just one species of red fox.

The case that these two types of red fox are different species is just so much stronger than the island fox’s taxonomic distinctiveness.

Of course, I actually do question the taxonomic validity of the island foxes. Some of these island fox populations are so inbred that they could stand to have mainland gray foxes introduced for genetic rescue purposes, but because they are a species in the eyes of the Fish and Wildlife Service, no one seriously considers the possibility.

But when it comes to red foxes, two things are clear:

They are native to this continent and are not English imports.

And they haven’t exchanged genes with the Old World red foxes in a very long time.

So there really is a strong case that our red foxes are Vulpes fulva and not Vulpes vulpes.

But there aren’t wide morphological differences between the two populations. Red foxes in Europe pretty much look like the red foxes of the Eastern US. In fact, North American and northern Eurasian red foxes look much more similar to each than either looks like the Middle Eastern and North African subspecies of red fox.

Red foxes in Eurasia and North America pretty much share the same niche as generalist mesopredators. Both types have successfully colonized suburban and even urban environments.

Those are the traits we see.

But their DNA says we’re looking at two quite distinct populations.

It’s counter-intuitive.

But it is strangely fascinating.

 

 

 

 

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Red foxes are native to North America.

They were also introduced.

That sounds like a contradiction, but let me explain.

First, we should look at the North America red fox distribution map. Red foxes in North America have several subspecies.

Click to make larger.

Subspecies number 6 is Vulpes vulpes fulva.

It was traditionally believed that it didn’t exist until the seventeenth century, when English colonists introduced red foxes for hunting purposes.

I’ve often said that red foxes are not native to most of the Eastern United States and that they all derive from imports.

The trouble is that there have been few genetic studies on red foxes in the Eastern and Southern US that have made tried to figure out exactly where they came from.

Well, it turns out that this assertion may be wrong.  A recent mtDNA study revealed that North American red foxes, including those found in the Southeastern US, don’t have Eurasian red fox mtDNA haplotypes. That means that the matrilines of red foxes living in the Eastern US are derived from indigenous vixens, most likely those from Eastern Canada that colonized the United States in the middle of the nineteenth century.

Now, an mtDNA study cannot tell us everything about the genetic make-up of red foxes in North Ameriaca, and it is possible that some of their genetic material came from imported red foxes that were introduced in the seventeenth and eighteenth centuries.

A larger sample of red fox DNA is needed to see exactly what the ancestry of these foxes actually is.

However, this study is making me reconsider some of my assumptions about the local red fox population.

It’s true that red foxes weren’t here at the time of colonization. However, red fox remains that date to the time of time of the Wisconsin glaciation have been found in Virginia and Tennessee.  When glaciers retreated, the red fox moved north in Canada, where it remained until European colonization.

The traditional account states that red foxes in the Eastern and Southern US came from those imports, but there is a large gap between those introductions in the seventeenth and eighteenth centuries and the establishment of red foxes in this part of North America in the  middle of the nineteenth century.

It is possible that our foxes have a mixture of native and European blood.

But it is also possible that the imports never really became established, or if they became established, they became swamped with native red fox blood as they came pouring down from Canada. My guess is there never were that many imported red foxes. Foxes are wild dogs, and they would not have taken well to confinement on their way from England to North America. Further, foxes that evolved to live in a benign marine climate may not have been able to thrive in a place that has such extremes in heat and cold.

Compared to wolves and coyotes, we know next to nothing about how the different populations of red fox are related to each other. We’ve only recently been able to determine how coyotes colonized Virginia through the Great Lakes and Canada, and we’ve also been able to figure out that certain propose wolf species are actually derive from recent hybridization between coyotes and wolves.

These studies looked at a lot more genetic material than mtDNA haplotypes, and we’re going to need studies like these on red foxes to determine what their exact ancestry is.

But if our assumptions about red wolves can be challenged through extensive nuclear DNA studies, then our assumptions are likely to be challenged when we start looking at red foxes.

Maybe we should consider red foxes native to the Eastern US after all.

I think we need to see how much “native” ancestry they have before making that assertion.

But this mtDNA study is certainly a major affront to the tradition account of how red foxes colonized the Eastern United States.

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