Hybrid Vigour

[becks]

http://news.nationalgeographic.com/news/20...ngered-animals/

Breeding rare Florida panthers with Texas cougars created tough hybrids that one scientist calls the Arnold Schwarzeneggers of cougars.

And, like action heroes, these vigorous offspring may well rescue the Florida subspecies from extinction, according to Stephen O'Brien, an animal geneticist who co-authored new research on the North American big cat.

(See big cats photos and learn how to help the at-risk animals.)

Florida panthers are considered a subspecies of cougar, big cats found across the Americas that are also called pumas or mountain lions, depending on the region.

In the 1900s people hunted the Florida panther out of most of its southeastern U.S. range, driving the few remaining animals into rugged South Florida swamps.

Inbreeding within this tiny population caused heart problems and reproductive defects that would have killed off the Florida panther—deemed endangered by the U.S. Fish and Wildlife Service—by the early 21st century.

As a last-ditch effort, in 1995 the U.S. government released eight female cougars from a wild Texas population into Florida.

This cougar infusion increased the number of Florida panthers threefold, to about a hundred, said O'Brien, chief of the Laboratory of Genomic Diversity at the National Cancer Institute in Frederick, Maryland.

In addition, the offspring produced were genetically diverse animals that were stronger and lived longer, the 30-year study revealed.

Texas Cougars Shuffled Genetic Deck

Since the early 1980s, O'Brien and colleagues have closely monitored several Florida panthers via radio transmitters and microchips, occasionally anesthetizing animals to take blood samples. Those samples revealed a "marked increase" in DNA diversity after the Texan animals were introduced.

The team also measured survival rates of kitten litters and adult cats. (See pictures of Florida panther kittens.)

For instance, 23 out of 29 Florida panthers surveyed that were older than a year died between 2002 and 2004, compared with just 22 out of 47 hybrids, according to the study, published today in the journal Science.

The scientists also measured the animals' fitness, or ability to survive. One unusual measure of fitness, O'Brien noted, involved recording how a cougar reacted when the animal attempted to escape scientists' capture by climbing up a tree.

Most Florida panthers would cower in the tree. But trapped hybrids were more than twice as likely than Florida panthers to leap out of the tree and sail over the scientists' heads to safety, he said.

"Virtually every measure," he said, "showed the animals that had the mixed ancestry did better."

In a sense, releasing the Texan cougars restored the genetic flow that humans had interrupted, O'Brien added. In the 19th century, Florida panthers would sometimes mate with western cougars, naturally "shuffling the deck" genetically, he said.

"We don't feel like we've fiddled so much with nature, like making a hybrid between a lion and a tiger." (See pictures of real-life "ligers.")

Florida Panthers Not Out of the Woods

In general, the research shows that bringing in new genes to aid a failing population "can be deliriously successful," O'Brien said.

"It's really not rocket science—if you have enough habitat and don't inbreed much, millions of years of evolution have given these species what it takes to survive and to prosper."

Even so, conservationists can't yet say hasta la vista to the Florida panther's problems.

"It was a very bold experiment and it has clearly paid off," said Elizabeth Fleming, Florida representative for the nonprofit Defenders of Wildlife.

But "now is the biggest challenge of all: We need to conserve existing habitat for these animals, as well as allow them to expand into some areas of their former range."

A hundred animals do not make up a truly viable population—for the subspecies to make it, their range needs to be expanded into other parts of Florida, Fleming said.

To that end, her organization is working with landowners to buy conservation easements, which would allow the predators to move onto land dedicated solely as wildlife habitat.

Meanwhile, some male Florida panthers are already striking out into new territory themselves, Fleming noted. (See "Cougar Reports on the Rise in Eastern U.S.")

"One made it all the way to Georgia," she said, "only to be shot by a deer hunter."

I must have the dumb, isn't this like crossing poodle with labrador and continuing to have variations of that cross breed and then claim the breed is pure poodle?

[Shaar]

They aren't 'Florida Panthers' anymore, they are cross-bred/hybrids, so essentially, they have killed off the pure Florida Panthers anyway instead of saving them.

In relation to dogs, hybrid vigor is a real thing... in the FIRST generation. Once 2 of those cross bred dogs carrying defective genes are put together, the problem rears its head again.

I understand why they did it... the cancel out the problems like the heart defects, but wild animals aren't fussy about who their secual partners are and odds are they will double up on those genes and still produce heart problems... 8 new panthers aren't going to fix that, it would have to be on a MUCH larger scale and be controlled.

[LizT]

Interestingly, in book I recently read on "Breeding Purebred Dogs", Hybrid Vigour is referred to as a way of strengthing a line that is weakened by repetative line breeding. Basically 'out-crossing' on the occassion, rather than constant random out-crossing or constant line-breeding. It was stressed that they were not referring to cross-breeding of different dogs though.

I think with the pumas if it is a 'sub-species' of the same breed of animal only indiginous to another area, although there will be differences in the breed due to it's environmental evolution, it is still more of an 'out-cross' than a 'cross-breed"? However, either way you look at it, it's not the same animal. I mean wouldn't this type of thing happen, in part with migratory animals who all travel to the same breeding grounds?

Also interesting, is the fact that some male Florida panthers are travelling out, probably looking for new bloodlines and mates in which to continue their lines, as males do. Better watch out for those idiot "Deer hunters" who don't know the difference between a puma and a deer!

Edited September 29, 2010 by LizT

[Steve]

You get the same effect when you have one breeder who has tightly line bred for several generations and then goes out to another line with no common ancestors for many generations.

Not much point in doing what they have done without using other levels of science. That is still a closed population and within a generation or two the heart problems will still be there.If they did what modern dog breeders do and test the dogs and profile the pedigrees before they bring in fresh blood the results over a longer period of time would have been much better for maintaining the species rather than one generation which is less likely to suffer a couple of known recessive genetic issues. Anyone can breed one generation but when you need to ensure the health and temperament most suited for survival of a breed or species there's a lot more to it than taking an animal from a differnt geography and crossing your fingers that only the clears will reproduce.

The probable reason for the difference in behaviour is that cats in that area have been able to survive better by hiding out in trees rather than being more open targets for a shooter.So that type of temperament trait has been able to live long enough to reproduce while the others are bumped off by humans before they can get to that.

[raz]

one scientist calls the Arnold Schwarzeneggers of cougars.

Does that mean they need to take a handful of anabolics morning and night to stay big? Arnie wasnt called the pharmacist for nothing.

Interesting article though

[LizT]

one scientist calls the Arnold Schwarzeneggers of cougars.

Does that mean they need to take a handful of anabolics morning and night to stay big? Arnie wasnt called the pharmacist for nothing.

Interesting article though

No.... it means they will be running for Governor of Florida!

[raz]

;) After staring in some really bad porn, Pumping Iron and Konan the Numpty

Disclaimer - I'm actually a huge fan of the airhead.

Edited September 29, 2010 by raz

[LizT]

;) After staring in some really bad porn, Pumping Iron and Konan the Numpty

Disclaimer - I'm actually a huge fan of the airhead.

Me too...my parents are Austrian and Arnies dad was the local cop in Dad home town.

But remember......."It's not a Puma!" (read tumour)

[raz]

But remember......."It's not a Puma!" (read tumour)

;) Just lost my coffee

[shortstep]

They do not say how many original cougars were left, only that they brought in 8 new cougars.

Still, how fast the heart problem would come back or even if the heart would ever come back, would depend on how complex (the number of genes involved) the heart problem is and how genetically diverse (number of new different alleles available from the new population) the new cougars offer for replacement of the affected disease genes.

If the new cougars do not suffer from bottle neck and have a wide verity of different alleles to offer, and the heart problem in complex with a good number of genes affected, then there would every reason to believe that after introducing the new cougars, the disease would be so disrupted or you could say so diluted, that all the future generations would have very little risk of presenting with the same set of 'bad' alleles. Over time they may have even less risk, again depending on how diverse the new alleles on offer were.

Another words this would make the possible gene allele combinations so varied, as to make it unlikely that many if any of the the proceeding generations would inherit all the exact same 'bad' alleles. The very few that might be that unlucky to end up with all the bad alleles again would be a tiny number of the population and would be weaker and less likely to survive and reproduce. It could also be possible that any one of the 'bad 'alleles might be totally lost and replaced by the any number of 'good' alleles so the disease could never come back.

I do not see this situation as one simple recessive gene and the first generation is free of the disease but the second generation will inherited it right back again.

Most diseases, like most heart problems will have many genes involved. To replace all of the many new 'good' alleles now on offer with the single one 'bad ' alleles when there are no so many possible combinations on offer would be very difficult.

You would have to start all over again inbreeding and very strongly selecting to reduce number of possible alleles (and even then be lucky as these individual alleles are likely not something you could see and select for or against) to actually reproduce the disease again.

Think of it this way, lets say there are 8 alleles involved in the heart problem and the new dogs bring in 50 new allele possibilities to potentially replace the 8 'bad' alleles. The possible combinations over the generations are huge.

Another difference in this form of breeding is the selection process. These cats will be using survival of the fittest, so the cougars with the strongest genes (which will include good hearts) are the most likely to reproduce. There is no assumption that the affected dogs (cats with bad hearts) will stay equally represented in the reproducing gene pool. any bad heart cats would likely not be represented at all once the number of unaffected stronger cougars increases.

I see it as greatly increasing the genetic possibilities on offer, which reduces the risk of the disease now and if maintained as a diverse population would help to prevent it from coming back again as a significant problem in the population. At least that is how I see the possible long term benefit for the heart problem.

Another totally different question is are these still the Florida cougars. I really have no idea. But form follows function, so I would assume the cats with the new genes (strong hearts) would predominate as their study numbers showed. However the cats that had other features that helped them survive in their environment would also be selected. I would guess they would settle into one type of cat (over time) and that would be different from both of the original populations of cats.

Gees that was long winded and rambling, sorry.

I need more coffee!

[LizT]

Long winded and rambling perhaps, but definitely informative!

[LizT]

But remember......."It's not a Puma!" (read tumour)

;) Just lost my coffee

So you picked up my accent then....

[raz]

I did, Liz. That cracked me up.

[ash&elar]

They aren't 'Florida Panthers' anymore, they are cross-bred/hybrids, so essentially, they have killed off the pure Florida Panthers anyway instead of saving them.

In relation to dogs, hybrid vigor is a real thing... in the FIRST generation. Once 2 of those cross bred dogs carrying defective genes are put together, the problem rears its head again.

I understand why they did it... the cancel out the problems like the heart defects, but wild animals aren't fussy about who their secual partners are and odds are they will double up on those genes and still produce heart problems... 8 new panthers aren't going to fix that, it would have to be on a MUCH larger scale and be controlled.

I see them as the same species from diff parts of the same country, I would liken it to breeding an australian bred lab with a amercan or english bred lab, same breed just slightly different breeding etc. I think they have done a good thing.

[mackiemad]

that's how i read it ash.

or a black lab with a yellow lab.

or a short coat collie with a rough collie.

in essence they are the same breed that live in similar but different areas of the country. so a kelpie from NSW bred to a kelpie from SA...

shortstep: did they say that the population had increased threefold to one hundred? so does that mean there was 22 animals left and THEN the 8, or 30 and then the new 8 cats?

and i agree that just because there are 8 new cats it does not mean that any previous problems have been bred out, surely you would need selective breeding and a continuation of new, tested, blood/genes? also the jumping thing could be a learned behaviour from a mother, so if a introduced mother had that behaviour and passed it on to her litter of, say two kittens, then they would display that behaviour, whether or not they had an introduced father or not. whereas the cats that already lived there may never had learned that behaviour and so could not pass it on to kittens. just a thought...?

but hey, if it is working then kudos to them.

[Lowenhart]

There is some train of thought that genetically there is just 1 North American Puma, just given different names in different regions.

There is a paper published on that here.

I don't believe you can equate purebred dog breeding as being the same. Dogs are kept "pure" by strict human intervention, whereas if they were allowed to range there would be interbreeding where the dogs domain intersected.

If they can put the "Florida Panther" in a better position by using the same type of cat that lives in Texas then that is great. But they still have an uphill battle. I think it's an interesting project, and I hope they secure more land for the cats and keep them off the highways...

[shortstep]

I don't believe you can equate purebred dog breeding as being the same. Dogs are kept "pure" by strict human intervention, whereas if they were allowed to range there would be interbreeding where the dogs domain intersected.

Yes, and perhaps even more important, there is no survival of the fittest. We do not say to our pet dogs, go catch your dinner or you starve to death, go fight for your mate and win or no puppies from you and so on.

BTW I not sugesting nor do I think we want pet dogs to be bred by survival of the fittest selection. We do not want a dingo, wolf or wild african dog in our family room (well ok I might, but most would not), we want a domesticated companion pet dog bred to be just that.

[corvus]

I saw this more about increasing genetic diversity and boosting population numbers than hybrid vigour. We all know that increased genetic variation makes for healthier populations as a general rule. The heart problem was not the only one that was showing up from what I heard. I seem to remember stories about kinky tails and other such things. The only way I know of to fix inbreeding depression is to increase genetic variation at the population level, i.e. introduce new blood.

Whether it's the same subspecies or not anymore is a red herring of a question if you ask me. We were never sure that they were different in the first place, and the only thing naming species is good for is making sure we're all talking about the same critter. It provides a snapshot and nothing more. Populations are extremely dynamic and evolution of new species is occurring right in front of our eyes. You could spend a lifetime testing and retesting subspecies and changing their name and status to best reflect what seems to be happening at that moment. I think when it comes to panthers it's most helpful to look at them in terms of populations rather than subspecies, but that's just my opinion.