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Posts Tagged ‘hybridization’

dholes

We know that hybridization is a big thing in the genus Canis.  Indeed, scientists are still debating about the validity of certain species because some of the extant forms of wolf could very well be hybrids between gray wolves and closely related species. Everyone thinks that the large coyotes we see in the East are all coywolves, even though they don’t have that much wolf ancestry. but then we have very good genomic data that shows that coyotes and gray wolves really aren’t that different genetically.  We know that Ethiopian wolves were threatened with and still could be threatened with hybridization from domestic dogs, but we also know that getting dog genes into a wild canid isn’t always a bad thing. Wild gray wolves in North America got their black color variant from a single Pre-Columbian black dog that crossed into the population between 1,500 and 7,250 years ago in the Yukon or the Northwest Territories.

I have often wondered if we could detect hybridization that went on long before all these wolf-like canids truly diverged, and a recent paper in The Journal Cell reveals that hybridization has always been a feature of these wolf-like canids. Gopalakrishnan et al. compared the genomes of gray wolves, coyotes, domestic dogs, golden jackals, the African golden wolf, the Ethiopian wolf, the dhole, and the African wild dog to see if there was any evidence of hybridization in the lineages.

The authors found that the African golden wolf was actually a hybrid species that developed from gene flow between the gray wolf and the Ethiopian wolf, which likely had a much more extensive range in Africa than it does now.  The authors also found that the clade (which I think is actually a single species) that includes the dog, wolf, and coyote received genes from an unknown species of canid. The dhole and African wild dog have also hybridized in the past, probably because both the dhole and African wild dog once had ranges that overlapped in the Middle East or in North Africa.

The discovery of this unknown species is perhaps the most intriguing. The authors speculate that it might have been the dire wolf or the extinct North American dhole, but seeing that this species fairly close to the division between the dhole and African wild dog, I think a more likely candidate is Xenocyon lycaonoides.  This animal has been posited as an ancestor the dhole and the African wild dog, but a more convincing argument is that the African wild dog derived from Lycaon sekowei.  It is not clear yet what the dhole derives from, but it could have derived from Xenocyon or shared a common ancestor with it.

Xenocyon was the dominant wolf-like canid in Eurasia and Africa during the early part of the Pleistocene, but by the mid-Pleistocene, it began to become less common, and as its numbers dwindled, the diminutive wolf, Canis mosbachensis, began to fill its niche, eventually evolving into the modern gray wolf, which also led to the coyote and domestic dog lineages, as well as the hybrid African golden wolf.

Maybe, as the Xenocyon’s numbers dwindled, a few remaining ones hybridized with C. mosbachensis, perhaps introducing some genes from better pack cooperation and larger size that helped the smaller wolf fill the bigger canid’s niche.

The authors are clear that we need lots of ancient DNA from these extinct canids before we can engage in flights of speculative fancy, but seeing that this unknown canid was so close to the dhole, I think that this animal is a better place to look. Xenocyon might be a bit too old to find viable DNA in fossil remains, but it is certainly possible that we could find some.

So yes, hybridization has greatly affected the evolution of wolf-like canids in the modern era, but hybridization always has. Similar findings have been discovered in bears and various members of the cat family.  My guess is that virtually every clade will have had some of this going on, even if the current species do not hybridize.  Speciation happens, but chemical interfertility isn’t lost for quite some time after speciation. Gene flow continues on with related species, which continues to affect their evolution.

Yeah, evolution is a tangled bush that also has vines that reach out and grab adjacent and not so adjacent twigs.

 

 

 

 

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hybrid

The scent of canid estrus wafts out of the clouds of the Harenna Forest in Ethiopia’s Bale National Park. It floats out of the wet jungle into the land of lichens that lies way up high in the Sanetti Plateau, where he smells it.

He stops to savor the scent, which is almost like that of his mother and sisters but not exactly.

Yet is strangely beguiling.

His kind are the red-coated “wolves” of the Ethiopian Highlands. They are Africa’s rarest canid and may be the rarest of all wild dogs. They spend their days hunting big-headed mole-rats and other rodents. They are rare and found only in these Afro-Alpine lands of Ethiopia.

His kind stay in the open moorland of lichens. They don’t wander down in the cloud forest. That is the realm of the black leopard, the creature that savors the taste of dog-flesh above all others and would love nothing more than to swipe an arrogant little tawny wolf.

But the smell is strong, and the last few months have been hectic in his pack. The bitches have all come in estrus, and his mother ran off his older sisters. By the law of Ethiopian wolves, only one bitch produces a litter and that one bitch is the sole mate of a single male.

Thus, our wolf friend has spent a long time smelling the beguiling fragrance of estrus but never getting a chance to partake in any mating.

This smell isn’t quite the same, but it’s so similar that he can’t help be drawn to it.

He abandons his caution and wanders down into the clouds. He soon finds himself in the wet jungle of the Harenna Forest. Moss lies hard upon the trees.Strange little monkeys chatter among the bamboo.

And the scent grows stronger.

He keeps following his canine  concupiscence through this strange world. For a creature so devoted to living in the open moorland, this jungle is a terrifying alien landscape. The buzzing of insect causes him to jump. The gentle falling rain upon the leaves vexes him.

Hunger soon begins set in, but just as he’s about to turn around and head home, he catches wind of some decaying meat.

He follows his nose and soon finds himself looking at the remains of a bushbuck. He also smells the odor of a cat of some sort, but it has long since passed. But smells another odor. It almost like that of his own kind but not quite.

He is in the land of strange wolves, and his hackles are raised.

He knows he might have to fight for a bit of food, but he doesn’t know who these strangers are.

He eats a bit of the meat and raises his head to scan the undergrowth. He must eat, yet he is terrified.

He hears the approach of canine steps. He bristles. The time for a fight is now!

Then the beguiling scent of estrus fills the air. The hackles go down. He doesn’t consciously realize that he’s becoming softened.

The sound of canine steps grows stronger. They stop. Then they grow stronger again.

Then out from behind a stand of kokisa trees comes the creature. Our wolf notices that this is source of the beguiling estrus odor, and though he was expecting a strange Ethiopian wolf from another pack, she not one.

But in some ways she is.

She is almost entirely gray with black hairs mixed in. Along the sides of her back the pelt mixes in such a way as to form two stripes, each running from her shoulder to her hip. Her tail is tipped in white.

She is a side-striped jackal.  Her kind is numerous. They are found throughout Africa south of the Sahara and the Sahel. They are creatures of the brush and thicket. Their kind almost never makes it onto nature documentaries.

They are that banal, that common, that no one would would waste time filming a den-site or extolling their virtues.

Our two creatures stare at each other over the bushbuck carrion. Neither knows what to make of the other. 3 or 4 million years of evolution separate the two species. One is a specialist of an ecosystem that is dying. The other is a generalist of tropical Africa.

But the genetic difference between the two is trivial at this moment.

The young jackal bitch has been driven from her parents’ territory.  She is too defiant of her mother over the kills they scavenge, and her mother just can’t handle such recalcitrance. Estrus made the situation worse, for in jackal society, only one bitch and one dog mate and have the pups. Her sister accepted her mother’s edicts that only she would mother pups, but our jackal bitch fought back and tried to mate with her brother and then her father.

One big fight ensued, and now our jackal bitch is running through the forests, alone and in estrus. She has no territory, and no other dog jackals from other families have courted her.

Her desire to mate is strong now.  And though she’s has been eating off this old leopard kill– one that the old leopard decided wasn’t worth hauling up into the trees– she hasn’t been herself at all.

On her old leopard kill stands a jackal of sorts. He’s bigger than any jackal she’s seen before. He smells different, but he also smells good.

Part of her says to approach. Part of her says to flee. The former is pushing her forward, and as the wolf’s face begins to soften, she feels at ease.

She approaches the red stranger. They touch noses. She backs off.  He wolf-grins. She pounces at him playfully. He backs off. They stare at each other again.

The ritual goes on for an hour. They begin to forget what they are. The strangeness of the moment becomes an odd sort of familiarly.

She licks his lips. He licks hers.  He stands proudly with his ears back. She playfully paws him.

They smell each other.

She spins around and puts her tail to the side. He mounts. There is a tie.

For three days the eat from the bushbuck carcass and mate in the jungle. She alerts him to the scent of the leopard and shows him how much fun it is to chase monkeys into the trees.

On the evening of the third day, the young wolf stoops to drink from a puddle. The black leopard springs from behind a bush and is on the wolf before he knows it. The leopard doesn’t know that he has killed a rare wild dog. He’s caught a big jackal, and jackal meat is so tasty that he has to take it up into the canopy for storage.

The jackal bitch goes looking for her mate. She barks and howls into the night. There is no answer.

An old male side-striped jackal who hasn’t had a mate for year finds her. She still smells of estrus, so she is accepted by him. The two jackals wander off into the darkness. They mate one time, but the two remain together as mates. Within her grow the whelps, one of which is sired by the old male jackal, and the other is the hybrid with the Ethiopian wolf suitor.

The pups are born in the den she digs. One pup is a typical side-striped jackal, while the other is marked with tan points and a black tail with no white tip. The hybrid grows up as a jackal, though she is clearly different.

One day, a group of researchers comes across her and takes her photograph. Then they take many photos.

She is so strange that the researchers believe she is new species of jackal. When her photos are posted online, a lot of debate develops about what she is. Is a new species?  Is she a hybrid of golden jackal (now a golden wolf) and side-striped jackal?  Is she a  hybrid of Ethiopian wolf and dog?  Ethiopian wolf and side-striped jackal?  Nah. She’s an unusual side-striped jackal without the stripes or the white-tail tip.

And the mystery jackal roams the Harenna Forest. The debate goes on.

This is the story of a hybrid.

***

The above is an entirely fictitious account of what might have happened to produce the unusual jackal in the photograph above. The current consensus— based upon looking at the many photos taken of the creature– is that she is an unusual side-striped jackal.

The truth is this debate really can’t be settled definitely. We have no DNA samples from the beast.

But the possibility of other hybrids beyond the usual subjects in the genus Canis has long fascinated me. It could happen. It just hasn’t been confirmed anywhere.

Although the likelihood of this hybridization occurring is pretty low, it is very likely that the two jackals endemic to Africa, the side-striped and black-backed jackals, can hybridize. The two species usually fight with each other, but there could be instances where they have crossed.

We just don’t have as many genetic studies on these jackals as we do with wolves, dogs, and coyotes.

But I bet there are some interesting stories in the genetic history of these canids.

They just have to be explored a bit more thoroughly.

Jackals are a mystery waiting to be solved.

 

 

 

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