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Archive for the ‘Testudines’ Category

wild bactrian camel

Cladistic classification has some important implications for domestic animals. Because we classify taxa according to descent from a common ancestor, it is useful to place most domestic animals within the species of their wild ancestor. Generally, domestic forms are classed as a subspecies, so one will often see Canis lupus familiaris for the domestic dog and Equus ferus caballus for the horse.

I have noticed a strong resistance to classifying the domestic cat as a subspecies of the Lybica wild cat, but this resistance makes very little sense. We know that domestic cats come from a Near Eastern population of this cat, and domestic cats are not morphologically or behavioral that distinct from it.

But there are cases in which it is certainly appropriate to give domestic animals their own species designation.

The gayal or mithun, a domestic bovine that is found in South Asia. It has been given its own scientific name (Bos frontalis). but it has been claimed that is nothing more than domestic form of gaur (Bos gaurus).  The wild gaur is the largest species of cattle, but the gayal is quite a bit smaller. It is quite common for domesticated forms to be smaller than their wild ancestors, so this smaller size should be expected if the gayal is a domesticated gaur.

However, whole genome sequencing of the gayal has revealed that is a hybrid between male gaur and female domestic cattle.  It is thus a hybrid species that exists only in a domesticated form.

Because it has this hybrid ancestry, it rightly deserves its own species status. This species does not exist in the wild, but because it is a mixture of two distinct ones, it makes sense to place the gayal into Bos frontalis.

Another good place where it makes sense to have the domestic and wild forms as separate species is in the case of wild and domestic Bactrian camels.  The Bactrian camels, which are known for their two humps, are found in Central Asia.

A small population of wild Bactrian camels lives in parts of China and Mongolia.  Traditionally, these camels were classified as a subspecies of the domestic Bactrian camel, which is much more widespread. It was believed that the wild ones were nothing more than feral domestic animals. They might have been a relict population that never became domesticated, but the truth is we didn’t really know until quite recently exactly what they were.

Various DNA analysis suggest a divergence between wild and domestic Bactrian camels that has been estimated have happened 700,000 to 1.1 million years ago.  These findings mean that the wild Bactrian camels are a distinct species. They are not ancestral to the domestic ones, and they are not a relict population of conspecific Bactrians that never became domesticated.

So the domestic Bactrian camel is called Camelus bactrianus, while the wild one is called Camelus ferus.

It is in camelids that species designations get a bit tricky, because the literature has come up with quite contradictory phylogenetic trees for the evolution of South American camels.  The most well-known South American camel is the llama, and the llama is usually regarded as a domestic form of the guanaco.  Indeed, about the only thing the literature seems to agree upon is that the llama and the guanaco are closely related. However, I have seen papers that place the other two species, the alapaca and the vicuña, as being sister species or place the vicuña as being closely related to the llama.

I remain agnostic on how to classify the South American camelids until these questions are examined using a broader section of nuclear DNA. These four species all can hybridize and produce fertile offspring, and it is not exactly clear if they truly deserve to have two genera or not.

It may be that these four species as currently listed are deserving from a cladistic classification perspective, but it could be that some of these species are better classified as subspecies of one of the wild forms.

As it stands right now, I am holding out for more information before I will drop my two cents.

So when the domestic form is found to be a hybrid between two species, it is useful to classify the domestic form as a distinct species. When the domestic form is found to be highly genetically divergent from the extant wild form, it is also useful, and when we just don’t know yet, keep them as separate species until we have better answers.

We know what the wild ancestor of most of our domestic animals is, so we should be placing them within their wild ancestor’s species, if we are to adhere to cladistic classification.

But there are these curve-balls out there, and sometimes, it really does make sense to have a domestic animal as its own distinct species.

 

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Doe-eyed box turtle

She has pretty brown eyes:

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The big snapping turtle that has been menacing the duck pond all summer was caught. The neighbors saw it near the bank and caught it with a net.

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And the turtle is no more! Snapping turtles are legal in West Virginia now, and they aren’t even remotely endangered.

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The ducks won’t be afraid to go into the water anymore.

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I keep running into this female Eastern box turtle when I am out and about. She is usually out looking for a place to lay her eggs, and because I know that her particular subspecies could become threatened in the near future, I don’t even touch her.

At one time in my life, I would have taken her home. Most rural children in my part of the world collect box turtles during the early summer and try to make pets out of them.

The truth is that this subspecies, the Eastern box turtle (Terrapene carolina carolina), actually makes a terrible pet. They become deeply attached to their home range, and taking them from their home ranges stresses them so much that they become susceptible to disease and parasites.

The Eastern box turtle is a subspecies of the common North American box turtle, which used to range up into Eastern Canada as well as most of the Midwestern and Eastern US.  We know only about its range in Canada from remains that have been dated to the sixteenth century, but now it is experiencing lots of problems in its range in the US. In the neighboring state of Ohio, it is a “Species of Concern,” but it is still pretty common here. I’ve seen little, tiny hatchling box turtles that aren’t much bigger than a quarter, but these little turtles aren’t maturing many parts of their range.

So I don’t recommend that anyone keep pet Eastern box turtles, especially those from wild populations. Many states ban the practice now.

Even if you have a box turtle as a pet, it requires a large enclosure, a high protein diet, and relatively high humidity.

But not all box turtles subspecies have the same problem with attachment to their home ranges than the Eastern subspecies has.

In the South-Central US. there is another subspecies of the common North American box turtle, which is called the three-toed box turtle (Terrapene carolina triunguis). I first saw these turtles at a pet store in Vienna, West Virginia, and I was amazed at how much they looked like the native subspecies. The main difference was they were mostly chocolate-brown in color and had three-toes on their back feet.

three-toed box turtle

I didn’t know at the time, but these three-toed box turtles were being offered as pets simply because they were found to be much better suited to captivity than the Eastern subspecies. They still require the humidity, the large enclosure, and the high protein diet.

However, they aren’t as greatly stressed from being removed from their native ranges, and as a result they are much better able to adapt to captive conditions.

When a three-toed box turtle is released into my part of the world, they often cross with Eastern box turtles. I have often suspected that the Eastern one at the top of this page might be a hybrid, simply because she lacks the extensive yellow markings on the head.

But that could simply be a variation in the Eastern subspecies.

Whatever the story of these two box turtles is I think they can tell us a lot about how to think of wolves and dogs.

Modern wolves are very difficult to domesticate, and they make terrible pets. Dogs, of course, do very well in the human environment.

Just like the box turtles, there are minor morphological differences between wolves and the less exaggerated breeds of domestic dog.

And when given the opportunity, dogs and wolves exchange genes.

I do not know how much DNA Eastern and three-toed box turtles share. My guess is they share far less than dogs and wolves do, simply because dogs and wolves are a highly mobile, relatively large species and species with those characteristics tend to have less diversity as a species. Regional box turtle populations are going to show greater distinctiveness than a wolf or dog population when compared to the entire species.

My guess is that the split between the two subspecies happened earlier than the split between dogs and wolves, too. T

But it’s not controversial that Eastern and three-toed box turtles are just separate subspecies. However, saying the same about dogs and wolves tends to launch people. That’s because there are political and sociological reasons for classifying dogs as a separate species from the wolf, which you can’t say about the two subspecies of box turtle.

But if we’re willing to say that these two box turtles are part of a single species, what level of mental gymnastics are we willing to engage in to keep wolves and dogs separate species?

I know the answer to that question, I’m afraid.

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Some box turtles

Lots of box turtles over the past few weeks:

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Box turtles are not tortoises, though they appear to live like them. Unlike most species of tortoise, Eastern box turtles require high humidity and relatively mild temperatures.

They are actually quite closely related to aquatic turtles, but they can’t actually swim like the true water turtles can.

The local name for a box turtle is “land terrapin,” which is actually pretty good. On the East Coast, the diamondback terrapin was once a very common turtle that was often eaten.

Box turtles used to be commonly eaten as well, and I guess the meat is similar to the diamondback terrapin.

And they sort of look a bit a like.

It’s still better than calling the tortoises. In fact, a lot of box turtles sent to Europe as pets quickly died because they were kept in high heat, low humidity environments, which would be the correct way to keep many species of true tortoise.

The species isn’t rare in the least in West Virginia, but they are a species of concern in Ohio. Their trade is now strictly regulated through CITES, so they are far less common on the pet market than they used to be.

Last year, some idiot got caught selling box turtles across state lines.

So don’t think you can collect box turtles and sell them as a get rich quick scheme!

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Eastern box turtles need to be in the water a bit.

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