Archive for the ‘Taxonomy’ Category

tristan moorhen

Off the southeastern coast of Africa, the British Empire still holds onto some islands. The most famous of these is St. Helena, where Napoleon lived out his final days in his second exile thousands of miles from France and Europe and any trouble he might want to cause.

On two of these islands, though, a taxonomic controversy has brewed for decades. On Gough Island and Tristan da Cuhna, insular forms of moorhen (also known as gallinules in much of the US) existed.  They were smaller than the common moorhen, and they possessed shorter wings. In this way, they exhibited both insular dwarfism, a common trait of organism evolving on isolated islands, and the loss of flight that sometimes happens when birds evolve without selection pressures from predation to ensure flight in the population.

The moorhens on Gough Island, nearly 400 miles away, were quite similar to those on Tristan da Cunha, and in the 1950s, some Gough island moorhens were introduced to Tristan da Cunha.

These Gough Island birds did quite well on the new island. where an estimated 2,500 breeding pairs now exist. However, because these birds were introduced from Gough Island, they are not regarded as native and are not protected.

Traditionally, experts have regarded the Gough and Tristan moorhens as distinct species. The Gough species is called Gallinula comeri, while the extinct Tristan species is called Gallinula nesiotis.

However, over the years, it has been suggested that the two were of the same species, and the introduction of the Gough species was actually a reintroduction.

Not many DNA studies have been performed on these birds, but the most notable is Groenenberg et al (2008).   This study examined samples that have been collected over the past two centuries, including a specimen from Tristan da Cunha that was collected in 1864.

The authors found that the two forms were roughly genetically distant from each other as different subspecies of the common moorhen. Indeed, if one were wanting to keep the common moorhen a monophyletic species, one would be forced to include these two insular forms as subspecies of the common moorhen.

The authors found that the Gough moorhen had replaced the Tristan form, and they were different taxa. However, because their genetic difference was equivalent to the genetic difference between some common moorhen subspecies, the authors proposed that these two forms be regarded as subspecies, which they propose as Gallinula nesiotis nesiotis and G.n. comeri.

These birds are most closely related to African and European moorhens than they are to South American ones,

However, the debate gets fairly interesting here because the South American common moorhens are typically considered subspecies of a quite wide-ranging species. When the authors performed their research, the common moorhen was believed to have existed in Eurasia, Africa, and the Americas, but in 2011, the New World population was given full species status, which is usually called the common gallinule. Taxonomists fixed the paraphyly of the common moorhen by creating this new American species (Gallinula galeata).

But this study does not fix the controversy about the moorhens on Tristan da Cunha. Even if the Gough and Tristan populations constitute different subspecies, a real debate can be made as to whether the birds on Tristan da Cunha represent an introduction or a reintroduction.

And this is where the subjectivity part of taxonomy sets in. If the Gough subspecies behaves in the ecosystem in an equivalent way to the extinct Tristan subspecies on Tristan da Cunha, then one could just make the argument that the arrival of these birds in the 1950s was a reintroduction. If they behave in a fundamentally different way from the extinct Tristan birds, then they were simply introduced and certainly don’t require any special protections as a native species under the law.

But the subjective part is where to draw the line between being fundamentally similar or fundamentally different. Yes, the Gough subspecies is genetically different, and it may have some attributes that cause it behave just slightly differently from the extinct Tristan subspecies.

However one answers this question, one should keep in mind that it cannot answered so easily.

This debate is quite strong, not just in gallinules and moorhens, but a big debate exists within some quarters as to whether the feral horses of the American West represent a rewilding from the Pleistocene. Horse evolved in North America and then became extinct at the end of the Pleistocene, but a huge debate exists on how to classify the various late Pleistocene horses. They may have been a single species that was very close to the modern horse. In which case, the feral horses of the American West might be argued to be rewilding population. A more recent study on cheek teeth and ancient mitochondrial DNA of these horses revealed there were three species of horse in North America at the end of the Pleistocene, one of which was very close to the modern horse.

But the Pleistocene ended around 10,000 years ago, and the ecosystems that maintained horses on the range no longer exist in the same way. In this case, one could not honestly say that this was a rewilding. It would be an introduction. (That’s where I stand on the horses as native wildlife controversy.)

However, I’ve often thought about what would happen if we somehow got greater prairie chickens to thrive on the East Coast once again. A subspecies of the greater prairie chicken called the heath hen once ranged all the way down the coast from New England to Northern Virginia. It was a colonial staple, and it was hunted out of existence.

The last population of these birds lived on Martha’s Vineyard, and the last one died in 1932. Attempts have been made to introduce greater prairie chickens to the island in an attempt to restore something like the heath hen to the island, but these attempts have fails.  If such an attempt were successful, it would be very much like the replacement of the Tristan moorhen with the Gough subspecies.  A debate could be had as to whether it was was reintroduction or not, but at least it would be something.

So the story of the moorhens on these South Atlantic islands tells the story of a controversy. It is one that rages in the conservation community all the time. Can you restore an extinct subspecies by introducing another related subspecies?

That answer is never going to be fully black and white. Ecological as well as taxonomic considerations have to be examined. Otherwise, someone could easily make the argument that wolf reintroduction and conservation are silly ideas, because, well, domestic dogs are everywhere. Dogs are a subspecies of wolf, so they just replaced them.

So this controversy will rage hard as we try to deal with this nasty extinction mess. We don’t always have all the answers. We don’t always have the best solutions. But we need to think it through carefully. It’s all gray or grayish.

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qinling panda

Hundreds of species concepts exist, and within these concepts there are great controversies. As long time readers know, I am very skeptical of the validity of the red and Eastern wolves as distinct species, and I am even more controversial in that I think that the recent genome-wide analysis on coyotes and wolves have made question whether coyotes really should be thought of as a distinct species from wolves. I certainly don’t think it is controversial that wolves and dogs are the same species, but I’ve been drawn into long, drawn-out discussions about this subject.

If we accept these genome comparison studies (one that looked at wolves and domestic dogs and one that looked at wild North American wolves and coyotes), all North American Canis species, wild and domestic, have diverged from common ancestor within the past 50,000 years. There has been significant gene flow between wolves and coyotes across North America, including Alaska and Yellowstone National Park, where the wolves are said never to breed with coyotes,  and there is even more significant gene flow between wolves and domestic dogs in Eurasia.

These animals do not fit Ernst Mayr’s concept of species at all in which reproductive isolation is the most important feature. A species is a population of organisms that can reproduce and bring about fertile offspring.  Wolves, dogs, and coyotes can do these things.

Mayr’s concept has been criticized quite a bit because there are things that do reproduce and produce fertile offspring, but it doesn’t happen very much. Further, these two species could have been distinct for a very long time, such as the Grevy’s and plains zebra, which split about a million years ago but still are capable of producing fertile offspring.

Further, we’ve since gone into a different way of classifying animals in which descent from common ancestry is more important than arbitrary lines based upon more subjective features. This newer way of classifying organisms is called cladistics, and it fits with a way of organizing life that is deeply appreciative of evolution.

I prefer this way, but it certainly leads to controversy. If I say that dogs are wolves, am I endorsing an entire ways of viewing them that aren’t science-based at all. The arguments for strict dominance training models are based upon poorly designed studies of wolves, and the arguments for feeding dogs raw meat and bones are also based upon an appeal to nature argument that dogs are wolves.

But I am not making those arguments at all. I am simply placing dogs within the proper clade to which they belong in the wild bush that we once called the tree of life. I think, more controversially, that coyotes should be given the same proper placement.

My arguments for this classification have to do with the fact that gene flow still exists among all three populations and their very recent common ancestry.

This classification has to be put into perspective. For example, Old World and North American red foxes split from a common ancestor some 400,000 years ago.  A very good case can be made that red foxes are actually two species, just based upon that genome-wide analysis alone. There has been virtually no gene flow at all between the two red fox clades, except in Alaska, where some Old World foxes introgressed into the New World population there some 50,000 years ago.

There are also other species of large carnivora that ought to be recognized if we were paying a little more attention. The leopard of Java, commonly thought of as a insular dwarf of the common or spotted leopard, may have diverged from the rest of their species some 800,000 years ago. More recent estimates suggest that they split off about 600,000 years ago,

This leopard is not commonly thought of as a distinct species, but it is likely multitudes more distinct than wolves, coyotes, and dogs ever could be from each other. More study does need to be performed, of course, but it seems likely that the Javan leopard really is its own thing.

Perhaps the most compelling case for a hidden species in a large carnivoran that I’ve seen is the case of the Qinling panda. Currently, two subspecies of giant panda have been recognized in China. The more common type is black and white. It is the one commonly on loan to zoos in the West, and they are the pandas I saw as a boy at the Cincinnati Zoo.

But there is also a rarer form that is found only the Quinling mountains. It was always thought of as odd because it is brown and white, rather than black and white.  Because it is such an isolated population it was long suggested that its brown and white coloration was the result of inbreeding, and that may still be the case.

In 2005, this brown and white panda was given its own subspecies, usually just called the Qinling panda.

Full genome comparison of both forms of panda have revealed that they are quite distinct from each other. The two forms split 300,000 years ago,

Full genome comparisons revealed that coyotes and wolves split only 50,000 years ago. The same analysis revealed a much, much deeper division in giant pandas. Genomes revealed that there is a panda that really should be its own species. Call it the Qinling panda or the brown panda.

But moving this animal to a full species would mean that we have a very endangered species. There are no more than 300 Qinling pandas in the world, and it could be quite difficult to protect them.

The coyote and red and Eastern wolf problems revealed in genome comparisons are also quite complex. The coyote is in no way endangered. It has vastly expanded its range since European settlement– pretty much all of North America but the High Arctic has coyotes now.  The red and Eastern wolves have genes from now defunct wolf populations. Both of these wolves will continue to cross with coyotes, and the only way to keep them from becoming totally swamped with coyote blood is to keep coyotes out of their ranges, a nearly impossible task.

Meanwhile, Eastern coyotes with wolf ancestry are evolving larger bodies. They are refining pack-hunting behavior.  They are evolving into a sort of larger, pack-hunting wolf on their own.

What this means for wolf taxonomy and wolf conservation is really a complex question, but I don’t think this question can be answered until we fully account for the problems caused by both the recent split of wolves from coyote and the continued gene flow between them.

It is a question that really cannot be answered unless we’re looking at the broader picture.  They are nearly as distinct from each other as many other animals that we are conventionally classifying as a single species now.






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Consequential taxonomy fail

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I believe I can identify the mystery “deer” that was mentioned on the Fortean Zoology blog. It’s not a deer at all.  Instead, I think it is the creature featured below.


I think it’s a female steenbok. (Compare with this close-up. And this one.)

Female steenbok.

Female steenbok.

Steenbok are a common game species that are often taken by big game hunters. They are native to areas that were easily accessed by Europeans during colonialism, and even today, sport hunters take them.

If it’s not a steenbok, then it is an oribi, which is a somewhat larger antelope. It has a larger distribution in Africa, but I think the typical oribi has more white on its face than the typical steenbok. That’s why I’m wagering that it’s a steenbok.

However, old taxidermied specimens don’t often have all of the identifying marks of the living animal. My guess is that this animal had larger ears when it was alive. Some of the less arid races of steenbok have smaller ears.

I don’t think it’s a gray or common duiker, because the head shape is all wrong. The female common duikers have black marks on their heads, which demarcate scent glands. The red forest duiker lacks the lighter marks around the eyes, and it also has the wrong head shape. All the other red or reddish duikers have rather longer faces than this specimen does. I don’t think any have those lighter marks around the eyes.

So the “deer” is actually some species of small antelope from Africa– most likely a steenbok (which is not to be confused with what the Dutch call a “Steenbok”– that’s an ibex.)

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