Advertisements
Feeds:
Posts
Comments

guatemala black howler

Hybridization between species is aspect of evolution that is only just now becoming recognized as a force in evolution. It is sort of taking a biological app from one species and adapting it another, and most studies on this phenomenon look at the app adaptation aspect of hybridization.

However, hybridization is more often than not less advantageous from a natural selection standpoint. Although these “new apps” and heterosis might be good for hybrids, many hybrids are sterile. Or if they aren’t sterile, one sex will either be absent or sterile.

Species generally have mechanisms that prevent hybridization. Many of these are behavioral.   For example, related bird species often won’t exchange genes because the female are simply not attracted to the males’ songs.  But there are molecular responses against hybridization as well.

One of the most contentious hypotheses about hybridization between species is that of reinforcement. What this hypothesis contend is that when two species begin to hybridize readily, there will be a strong selection for greater genetic distance between the two hybridizing species. With greater genetic variation, it will be less likely that the two species will be able to produce viable offspring, and over time, there will be fewer hybrids in the population.

This hypothesis has not been tested much. However, a study of two species of howler monkey in the Mexican state of Tabasco revealed that, yes, reinforcement is a thing.

Mantled and Guatemalan black howler monkeys diverged from a common ancestor about 3 million years ago. The two species have only a narrow contact zone, which is thought to have formed only 10,000 years ago in this tiny part of Mexico.

The researchers examined loci of the genomes of specimens of both species, including those in the hybrid zone. They found that the genetic difference between the two species was greater at the hybrid zone than from monkeys that lived in other regions. This discovery supports the hypothesis of reinforcement.  The greater genetic difference between the two species at the hybrid zone means that this greater genetic difference likely has evolved as a way of keeping the two species from producing lots of hybrids, which might not be as fit or  as good at reproducing in the wild as pure ones.

This discovery of reinforcement means that we have another tool in sorting out whether two species make sense. If we discover that there is greater genetic difference at a hybrid zone between the two species, then we know that they really are quite taxonomically distinct.  If we find the opposite, it means that hybrids aren’t deleterious in the population, and hybridization is either advantageous or neutral for the populations.

Yes, I would like to see this hypothesis tested on the various hybridizing canid populations in the gray wolf species complex. My guess is that it doesn’t exist in these animals, because hybridization isn’t that deleterious. And the genetic divergence isn’t that great to start out with.

But this study gives us a good idea of how hybridization operates in populations, and how some populations evolve to restrict gene flow.

Advertisements

jolly ball the best ball

forest dog

cheetah

India’s supreme court is now seeing an interesting case in which taxonomy and endangered species politics converge to have real world consequences. The question is whether African cheetahs can replace Asiatic cheetahs on India’s plains.

Yes, for there were once cheetahs in India. Their traditional quarry was the blackbuck antelope, and many nobles in India kept cheetahs or “hunting leopards,” as the British colonizers called them, for coursing blackbuck.

Cheetahs were not just found in India.  They ranged throughout the Middle East up into the Caucasus and Central Asia. In the wild, this lineage of cheetah is found only in Iran, where they exist in only relict numbers.  In Iran, the situation is made even more complicated with an international human rights scandal in which several cheetah researchers were imprisoned.  Cheetahs have since been extirpated from all of Asia, except for that tiny Iranian population.

So India, a nation with growing wealth and a growing conservation ethic, cannot turn to Iran to reintroduce its former cheetahs.  With Iran out of the question, some experts have suggested that African cheetahs be used as stand-ins.

And this is where things get interesting. African cheetahs are not exactly like the ones in India. There is a bit of a debate about when the two lineages of cheetah split, with one set of papers and researchers suggesting a very recent split (5,000 years ago) and another suggesting a more ancient one (44,000-47,000 years ago).

40,000 years suggests way too much evolutionary distance between the two cheetah populations for African cheetahs to be equivalent of the Asiatic ones.

But even if we accept this later date, it is still not that much of a divergence. Currently, most experts recognize only a single species of red fox, but Old World and North American red foxes diverged 400,000 years ago.

African cheetahs have evolved to hunt on open plains. Various small antelopes comprise the majority of their diet. They are not ecologically that different from cheetahs that lived on the plains of India.

So they aren’t that genetically distinct from each other, and they aren’t ecologically that different either.

It would make sense to bring African cheetahs to India. Of course, the legal system and the interpretation of statutes often goes against sound conservation policy.

But if cheetahs are ever to return to India, the question is now in the hands of India’s supreme court.

I hope they decide that those from Africa can stand in. They are far from exact, but they are far from ersatz.

 

looking good

Head tilt

Patented German shepherd head tilt.

cropped-dare-head-tilt.jpg

Dogumentary TV is a channel I generally like on Youtube, and I’ve watched it since it was called “Bully Badass TV,” when it was mostly about American bully subculture. (American bullies are blocky-headed, very-toned down offshoots of the AmStaff and American pit bull terrier breeds).  It is sometimes quite good, especially when Zeke interviewed my friend Brad Anderson.

Recently, Zeke purchased an FCI-strain Rottweiler pup named Roscoe, and he’s been doing this series about why he chose a Rottweiler over another breed.  This week, he posted about why he chose a Rottweiler over a German shepherd.

Ten years ago, I would have chosen a Rottweiler over a GSD. All of my experiences with Rottweilers were good, and none of my experiences with German shepherds were good. I lived where there were a lot of fence barking GSD, and there were quite a few that were known for biting. Rottweilers were mostly just good ol’ farm dogs.

But as people know, I’ve totally changed my mind about German shepherds. And I blamed the blasted dogs for this embarrassing turn around. These dogs fit my personality better than any other dog I’ve spent time with.

I don’t have anything against bite-work bred GSD, and it was actually one of these dogs that changed my mind. But her high energy and high levels of dog aggression made it very hard for us to manage in a house full of delicate sighthounds.

The really well-bred show dogs, though, really do fit well into our house. They are not dog aggressive. They have a lot of drive, but they have an off-switch. Quest can bark and look intimidating, but he’s not particularly dangerous.

So I do like these show-bred German shepherds. You may hate me for it, but I always have reserved the right to change my mind when I’m presented with more compelling evidence.

One reason I hated show GSD is really the big reason that Zeke decided to blast the show dogs. Yes, I know that Zeke knows mastiff and mountain dog-type dogs better than herding breeds, but in this installment of Dogumentary TV, he decided to say that the show German shepherds have bad hips because of their rear angulation.

You can hate their rear angulation all you want, but their hips do not contribute to their rears. Indeed, the truth of the matter is the hips on American show-line German shepherds have steadily improved over the years, because breeders have paid really close attention to this issue. They still breed for the flashy rears, but they also breed for good hips.

I’ve taken in a few randomly-bred and poorly-bred working-line GSD over the past year, and we’ve had their hips x-rayed.  Not a single one has had anything that could pass OFA.

I know Zeke prefers mastiff-type dogs from an aesthetic perspective. I personally don’t, but that’s okay. He doesn’t like dogs that shed very much, and he’s very right to avoid this breed if he wants low shedding.

However, he’s used the classic formulation of show vs. working GSD that is guaranteed to set a dog up for failure. When we say that the show dogs are all a mess and that they cannot walk because of their bad hips, we aren’t just wrong.  We are setting up a disaster.

If you tell the average person that they need to get a German shepherd without the extra rear angulation, they will go to the bite-work bred dogs. There are breeders who produce quality ones, but they are not cheap. There are also many more breeders who are breeding bitework dogs with very little health testing and often without working tests as well. Haphazard breeding of dogs with this amount of energy  can result in animals that are quite hard to live with.

He is quite right in saying that he’d avoid the working German shepherds that he has met because of their energy level.  But he’s quite wrong that the show-bred dogs are this level of mess.  Getting the temperament right on a dog that can bite people and still be safe to have in public is not easy, and the typical dog owner cannot give a really super active working dog what it needs to thrive.

What is even more disappointing is that he showed American show German shepherds in several short slow motion clips, all of which showed the dogs in awkward positions. He did not show a single dog in full gait. The American-style gait is free flowing, and one of the most beautiful sights in all the dog world. It is seeing this gait in person that changed my mind most profoundly about  what I thought about American show-line German shepherds.

Just for the record, here are the hip x-rays from Quest’s OFA prelims. He was designated as OFA Good for hips and normal for elbows.

quest's hips

Here is Quest playing around. He is one of those “slopeback cripples.” He has a lot of power in those back legs, though. He can launch himself way out into a lake to fetch a ball or stick.

shot put quest.jpg

Dogumentary TV is a well-produced Youtube channel. I enjoy many of the installments. Ultimately, though, a lot of the information one gets from the channel is up to the “expert” Zeke interviews. Some of these people know a lot. Some are into blowing lots of smoke, and unfortunately, he has bought into the “sloping back = bad hips” nonsense that some working-line breeders and internet personalities promote.

So I wish that Zeke would interview a breeder of German shepherds who does produce for the AKC show ring. He would do well talking to someone who breeds SV dogs for sieger shows as well. Both AKC and SV conformation lines have been selected for better hips. The SV requires it for all breeding stock, and the best AKC show breeders are constantly getting x-rays and DNA tests.

No one is trying to breed a dysplastic dog on purpose.

And yes, I used to believe all this stuff, but I forced myself to be objective. That’s the toughest thing in the world of dogs. Objectivity.

And yes, I know that Zeke is not really a German shepherd expert. He always leaned more toward the harder-edge mastiff and mountain dog breeds than I ever will.

I also have learned as I’ve grown up in the world of dogs that I don’t know everything, and I can be profoundly wrong about something. In fact, I was so wrong about German shepherds that I had no idea that this was the actual breed for me.

When something like that happens in your life,  you begin to wonder about other things in which you might still be in error. That’s one reason I hold back so much on the dog blogging these days.

I can still be controversial about dogs, but I now know I must be more diligent about what I think is true.

So that will hold me back a bit, but it will be for the better.

I wish Zeke the best of luck with his new Rottweiler pup. He looks like a really nice dog with great genetics.

And I think he made the right decision, but I still wish he would educate himself a bit more on why German shepherds have their particular conformation and how this does relate to their exact hip joint formation. It’s  just not related to the slope of the back.

You can like it or hate. But the extended rear angulation and sloping back are not the cause of bad hips in German shepherds. No credible expert actually believes that the two factors are related, because there are many dogs with sloping backs and extremely angulated rears that have super hips.

Yes, I’m aware that this is an age-old dog controversy.  But we have enough data from actual show dogs to show that this association between sloping backs and angulated rears and bad hips is not of a causal nature.

Hate ’em all you want.  But it’s not a health or welfare issue.

 

 

%d bloggers like this: