Feeds:
Posts
Comments

Posts Tagged ‘Somali wild ass’

Feral donkeys on Bonaire.

Feral donkeys on Bonaire. 

The Nubian wild ass hasn’t been seen in the wild since the 1950s. The subspecies has been presumed to be extinct. It lived in the Red Sea Hills and the Atbara region of Sudan.

Based upon ancient mitochondrial DNA analysis, it was revealed that there were at least two wild populations that are the source for domestic donkeys. The Nubian wild ass was the source one of the clades of donkeys, and the other came froma mystery population. Somali wild asses, the other extant subspecies of African wild ass that actally still can be found in the wild, is not a source for mitochondrial DNA diversity in domestic donkey.

I say all of this right up front, because what I am about to discuss are the limits of using mtDNA analysis to determine the relationship between populations, especially when one is trying to figure out whether feral population has some taxonomic distinctness.

The Dutch Empire still holds steadfastly to some islands in Caribbean. Among these is Bonaire, which is located just north of Venezuela. On that island is a population of feral donkeys, and the current excitement is the possibility that these animals might be pure Nubian wild asses.

If they are, they could be the very last of their subspecies, which is pretty amazing.  Keep in mind that there is no real historical context I can think of that connects an island off the coast of Venezuela with Sudan. Now, it’s certainly true that the Dutch colonists were connected to an empire that was all over the Indian Ocean, and the same can be said about the British and Spanish, who also occupied the island at various points in its history.

But even if they were connected across these maritime empires, why would anyone bring wild donkeys to an island and turn them loose?

And that brings us to the evidence for the Bonaire donkeys being Nubian wild asses. This is where mtDNA alone analysis can cause problems.

Researchers at Texas A & M performed an mtDNA analysis with samples from some Bonaire donkeys, samples from Nubian wild asses that were part of museum collections, sequences from four Somali wild asses, and one sequence from a domestic donkey that was available from the National Center for Biotechnology Information.

The results showed that the Bonaire donkeys were very close to historical Nubian wild asses and very different from the Somali wild asses and the domestic one.

I looked at the cladogram set up from the mtDNA analysis, and my curiosity was piqued. The domestic donkey’s mtDNA didn’t fit with the Nubians, but we do know that a lot of domestic donkeys actually do descend from Nubian wild asses. Nubian wild asses are a source for their mtDNA diversity, as I mentioned earlier.

But this NCBI sample wasn’t from the Nubian population.  Remember that the study I linked to earlier showed that some domestic donkey mtDNA sequences came from an undocumented population that was neither Somali nor Nubian. This particular sample could have come from that mtDNA lineage in domestic donkeys, but if they had included those that had Nubian ancestry, my guess is things would get complicated fairly quickly. The domestic donkey was used as a control, when in reality the best research method would have been to include a lot of samples from domestic donkeys in the study.

For some reason, this just wasn’t done.

Occam’s razor suggests to me that these donkeys aren’t Nubian wild asses after all. If more samples of domestic donkey are included in the analysis, I bet there will be several of them that come up very close to Nubian.

This is why we have to be careful of mtDNA-only studies, and the researchers at Texas A&M may not be aware for the new data on donkey domestication. Some donkeys have Nubian wild ass mtDNA, and others have mtDNA from a mystery wild ass population, which is not of the Somali subspecies.

We need more evidence to see if what the Bonaire donkeys are, but I think it is a very giant leap to call them the last Nubian wild asses.

Of course, what prompted this study is that late last year, the government of Bonaire was going to institute a donkey cull, which, of course, upset animal rights groups. With this analysis by Texas A&M in hand, the government was forced to halt the donkey cull.

However, the evidence that these donkeys are “pure Nubian wild asses” is nowhere near as convincing as it sounds.

I would like them to be. Don’t get me wrong.

But I’m not betting on it.

 

Read Full Post »

Analyses  of African wild ass MtDNA have confirmed the identity of one of the ancestors of the domestic donkey.

It turns out that the very rare and possibly extinct Nubian wild ass is the ancestor of one the two genetically distinct groups of domestic donkey.

The ancestor of the other genetically distinct group is unknown, but it has been confirmed that the mostly solitary Somali wild ass is the ancestor of neither of these two groups. The exact identity of this other group is still up for  speculation, including some “wild ass” guesses.  (If you don’t like these jokes, then you probably think I’m an ass after reading this post.)

These studies confirm that the first domestication of the donkey occurred somewhere in North Africa around 5,000 years ago.  This finding is pretty interesting, because no other large African mammal has been domesticated.

What’s more is that the researchers found that domestication was an ongoing process. The Nubian wild ass was domesticated several times, and there was always a gene flow between the wild and domestic populations.  This finding is not entirely different from what we’ve found out about dog and wolf populations.

Now, the identity of the other ancestor of the domestic donkey is still a mystery. This is not actually all that unusual. We still do not know which population of wild mouflon is the ancestor of the domestic sheep and the feral European mouflon. In fact, it has only been recently that the European mouflon has been recognized as a feral sheep and is not part of Europe’s native fauna. The exact ancestral wild sheep is probably extinct.

And in this way, donkeys and sheep share a history. The Nubian wild ass is often thought of as extinct in the wild. No one has seen one since late the 1990’s.

But because it went extinct only recently, we can make comparisons using DNA extracted from recently deceased specimens.

It is certainly interesting that the MtDNA studies found this relationship. I am very curious about the identity of the non-Nubian wild ass-derived donkeys. I have not seen the study, and I am wondering whether Asian wild asses might be that ancestor.

I honestly don’t know whether onagers and kiangs can hybridize with domestic donkeys or whether these hybrids are fertile. I also don’t know whether all the different species of ass were included in that study or if all the different subspecies of African wild ass were included. I have not seen the study, but if one of my very well-connected readers could find it and send it to me, it would be very nice.

Of course, one must be careful with reading too much into MtDNA studies. MtDNA may be least prone to mutation, and it is very useful in tracing matrilinear inheritance.  However, it is only one part of the genome, and there are no genome-wide analyses of the donkey. MtDNA is but one part of the genome. It’s useful for its purpose, but one must be careful in reading too much into it.

Remember, the MtDNA studies in domestic dogs strongly suggested that they were derived from East Asian wolves, specifically a South Chinese population. The genome-wide studies found that this simply was not the case.  Using SNP-chip technology, it was found that Middle Eastern wolves were much more similar to domestic dogs than an East Asian population of Canis lupus.

So these are interesting findings, but we need to be cautious about accepting this finding as the final proof.

Still, it shows how important donkeys were in the founding of civilization. We Americans like to think our civilization was built on the back of a horse. It is true. However, world civilization has mostly been built on the back of the donkey.

Where I live donkeys are kept for one purpose: livestock guardians.

One can drive down any rural road in West Virginia and come across small herds of beef cattle. Usually standing in the midst of those cows is a donkey. The donkey’s job is to keep the coyotes and stray dogs out of the pasture– a job they would take seriously even if there were no cows there.

As a general rule, donkeys hate anything that looks like a dog.

The next time I see one of these guard donkeys, I’m going to think of their wild North African ancestors– one extinct and the other unknown. I’m going to think of the ancient civilizations that relied upon these animals to build their marvels and to grow the grain that fed their populations.

I’m going to salute the donkey. I’m going to look at it with wonder.

We would probably be nothing without them.

And now that we no longer need them in my part of the world, it is good to know that they are being put to some use. Guarding livestock from canine predators is really not that hard compared to being a beast of burden, as they are in so many parts of the world.

Compared to their counterparts in poorer countries, most American donkeys have it good.

And that’s no wild ass speculation.

Read Full Post »

%d bloggers like this: