Natural History

As regular readers know from reading this blog, I am very skeptical of splitting species. I have yet to be presented with convincing evidence that there is more than one species of Holarctic wolf.   I do believe the Ethiopian wolf does represent a distinct species, as do the coyote and golden jackal, but all the other things called wolves– save the maned wolf of South America and its cousin, the extinct Falkland Islands wolf– are part of a very diverse species that includes domestic dogs, dingoes, and New Guinea singing dogs. At one time, I thought the red wolf was part of these species, now it should be considered part of the coyote species. It is nothing more than a glorified Eastern coyote.

So at what point do I accept the validity of a new species?

I don’t think that mitchondrial DNA studies can answer this question.  My issue with mtDNA studies is they often are quite inaccurate. Take the East African subspecies of black-backed jackal. Individuals within this subspecies have very wide variances in mtDNA, but they mate with each other. That’s why I’m very skeptical about the notion that some Indian wolves and some Tibetan wolves represent unique species. Mitochondrial DNA is maternally inherited. It is only a tiny part of the genome, and it is possible for unique and ancient matrilines to exist within species.  Using mtDNA analysis alone, we underestimated when savanna and forest African elephants split from each other.  They are actually quite distinct species.

The nuclear DNA studies on wolves have not found any evidence that Indian and Tibetan wolves are a unique species.  No study has specifically looked at these wolves, but the study that found the red wolf to be a coyote also found that South Asian wolves were closely related to Middle Eastern wolves. The pallipes wolf is quite widespread throughout the Middle East and South Asia, so it would make sense that these wolves would be related. No study has looked at wolves with these unique mtDNA sequences, but I’m very skeptical about their species status.

What we actually need is analysis from nuclear DNA. And we need a relatively large sample of that DNA.

I am someone who is deeply fascinated by taxonomy.

I also love the idea of finding new species. As I noted earlier, we aren’t likely to find too many new species large carnivorans.

When I said that, I meant that we wouldn’t likely find them in the field.

But we might find them in the laboratory.

The latest large carnivoran species to be documented was actually discovered in this manner.

For centuries, it was widely accepted that the clouded leopard of Southeast Asia, China, and Indonesia was a single species.

It’s a very elusive cat, and despite being called a leopard, it’s actually quite distinct from the common leopard species. It is a highly arboreal, and it possesses some unique tree climbing abilities that no other “big cat” has. It can climb upside down on the underside of branches, and it can descend from a tree head first.  Like most arboreal species, it has a long tail and short legs. The long tail helps the cat balance on the branches, while the short legs keep its body and center of gravity close to the branches and tree trunks that it is climbing. Using these adaptations, it is able to pursue prey in the canopy much more easily than other cat species.

Not much is known about the evolution of the clouded leopard. The clouded leopard weighs only 30 to 50 pounds, but it possesses canine teeth that are the same size as those of a lion or tiger. Because of these big teeth, some zoologists thought that clouded leopards were derived one of the saber- or dirk-toothed cats.

However, this theory has generally been rejected.

It is now believed that the clouded leopard is derived from some basal form of big cat, which did prey on large prey and thus needed large canine teeth.

But it’s just as possible that a predatory cat that kills relatively large prey in the canopy needed large canine teeth to make a quick kill. After all, a 30-pound cat that catches a 15-pound monkey on a tree branch is going to need to kill it quickly. If there is a big fight between predator and prey on the branch, the chances of the leopard being knocked off the tree are pretty high.

So maybe the cats evolved these big teeth as a way of killing arboreal prey rapidly.

These cats also attack deer, and cats of this size that kill deer, really need to be able to kill it fast.

So the clouded leopard is a big-toothed cat.

It is also the smallest of the “big cats.”   It is more closely related to the pantherine cats than the small cat species.

We’ve known this for a long time.

But what we didn’t know is that there were actually two species of clouded leopard.

How do we know this?

Well, there was a study that compared nuclear DNA, mitochondrial DNA,  and microsatellite loci of clouded leopards from the mainland and from Borneo. It also use the same methodology to analyze the genetic variance between different pantherine species.

It discovered that Bornean clouded leopards were as about as genetically distinct as one might find between different pantherine species.

This study used nuclear DNA and cytogenetic analysis. It was not merely a mitochondrial DNA study.

And these results were confirmed when mtDNA and microsatellite analysis was performed on Bornean and Sumatran clouded leopards.  The new species of clouded leopard is called the Sunda clouded leopard (Neofelis diardi), and the Bornea and Sumatran clouded leopards were recognized as two distinct subspecies. The mainland clouded leopard remains Neofelis nebulosa.

The two clouded leopards actually look quite distinct from each other.

Here is a Sunda clouded leopard:

 

This particular specimen was filmed and photographed at a preserve in Sabah. Sabah is on the island of Borneo, and it is part of Malaysia. It is the first specimen of Sunda clouded leopard to be filmed after the species was recognized as unique.

And here is a mainland clouded leopard:

The Sunda clouded leopard has lots of little spots within the cloud markings and the cloud markings are smaller.

It also is darker and possesses a double dorsal stripe.

Mainland clouded leopards have only a partial double dorsal stripe.

People had been looking at the pelts of these cats for centuries, but because the cats themselves were not as morphologically distinct as we see between lions and leopards, it was assumed that they were just variations within the same species.

But this is a great case of DNA analysis actually discovering a species.

The clouded leopards on Sumatra and Borneo were separated from the mainland species after the land bridge that connected those islands to Asia was submerged 1.4 million years ago.  The lineages split between 1 and 3 million years ago, and 1.4 million is roughly within middle of that range. However, what became the Sumatran and Bornean populations could have begun to develop their genetic distinctiveness as the result of genetic drift before the the land bridge was submerged.

The Sunda clouded leopard was likely wiped out on Sumatra when the Toba Volcano erupted about 70,000 to 75,000 years ago.  During the Pleistocene, sea levels were lower, so Bornean clouded leopards were able to recolonize Sumatra.

There is no gene flow between mainland clouded leopards and Sunda clouded leopard, and if there were, they might have issues with fertility.

But there is no gene flow between Sumatran and Bornean Sunda clouded leopards either, so those cats could become distinct species through genetic drift.

Islands are great incubators for speciation. All it takes is isolation and time– and enough genetic diversity within the isolated populations to maintain the population.

Islands don’t have to be in the ocean either.

Any physical barrier that prevents gene flow can create the isolation needed for speciation.