Site-specific frogs: is it possible?

[edwardsatc]

Toby,

Have you read the management plan outlined in the ASN handbook? Have you read the scientific literature? It doesn't sound like you have. The methods and models used are well (nearly universally) accepted by the conservation, ecology, and evolution communities. There are mountains of literature on this, this isn't just something that the frog community and TWI concocted. It is well based in the science. This stuff is taught in the most basic of Ecology courses.

Do you have any more specific argument, other than "survival of the fittest"? Can you point specifically to where the management plan or the methods and models described in the literature are wrong or deficient? Can you provide any empirical evidence to support your position?

I don't say this to offend and apologize if I'm wrong, but to be honest, your continued use of the term "survival of the fittest" and the context in which you use it makes me wonder if you really understand the concept of natural selection. "Survival of the fittest" is a very broad, general term that novices usually apply to to natural selection and doesn't really describe anything in specific.

To be honest, I had a long rebuttal to your comments prepared, but with the level of understanding demonstrated so far, it seemed like a waste of time. Additionally, if you haven't read and understand the management plan and the supporting literature, this discussion seems irrelevant.

[Toby_H]

I agree the quote for quote back and forth has gotten off track… I think keeping my point direct and concise will allow for clarity in understanding and response…




It is suggested we do not cull because culling differently than nature will alter the allele frequency… but “no culling” is still deviating from nature’s culling process…

How is “no culling” and “nature’s culling standard” offer the same results…


A lot of text above was spent arguing that we cannot cull to the same standard as nature, which I agree with. But this does not in any way explain how “no culling“ offers the same result as “nature‘s culling standard”.



It was suggested I review the Punnet Square Chart and I have… This is very simple so even if your not fluent with the chart feel free to follow along…


We are comparing a captive breeding program with a wild population, so we’ll need two charts…

Start both charts with the same breeding population that contains no aa’s and a few Aa’s…

Now on the wild chart, every time an aa is created, erase it. This will reflect the condition being lethal in natural environments thus these individuals do not survive to spawn… but in the captive chart do not erase it, apply it…

You don’t have to go very far to realize that eliminating something makes changes…

This will directly alter the allele ratio…


So in the case that a condition is lethal in wild population but is not lethal in captive environments… please explain how this example is inaccurate.

[Corpus Callosum]

Originally Posted by Toby_H

How is “no culling” and “nature’s culling standard” offer the same results…

A lot of text above was spent arguing that we cannot cull to the same standard as nature, which I agree with. But this does not in any way explain how “no culling“ offers the same result as “nature‘s culling standard”.

They don't offer the same results, that's exactly the point we are trying to make. In a conservation genetics when a captive population is managed in captivity we are not trying to mimic the selection pressures which exist in nature. We are just trying to retain as many of the original alleles as possible from the founder stock.

[spinycheek]

What if you can't get every frog to pair up? Allele maintenance seems to make the assumption that all animals will participate in breeding, but often, it seems individuals just aren't interested. Is there a way to squeeze out gametes like they do with salmonids?

[frogfarm]

With the few atelopus that seem to prove resistant to chytrid, is it a genetic resistance? How is the wild allele frequency going to look between the cb and wild pops in 50 years when those few individuals left in the wild start a new population? Aren`t you assuming there is no catastrophic change going on that will change the population or environment to a point where the cb stock won`t be good for repatriation efforts? Isn`t that exactly WHY were holding on to wc genes because they (pops and the environment)are changing?
Plus this shifting pairs, isn`t that dangerous? If there happens to be the next chytrid getting into one animal, over the time it will be transferred to all just like any sexually transmitted disease.
By chytrid I mean any disease that animals can act as a carrier for.

[MonarchzMan]

Originally Posted by Toby_H

So in the case that a condition is lethal in wild population but is not lethal in captive environments… please explain how this example is inaccurate.

It's a genetic snapshot. This is a real life snapshot, not a Harry Potter snapshot, so once it's taken, nothing changes, nothing moves. That's the definition of a snapshot. So when we take a founder population out of a wild population, we want to keep the genetics constant. Not change them because we will see a number of selective forces in nature, but we will miss many, many more. But that said, allele frequencies don't tend to change wildly in a wild population. It take a good amount of time to change frequencies, which is why maintaining a captive population that has the same genetics as the wild population at time of collection is good.

Originally Posted by spinycheek

What if you can't get every frog to pair up? Allele maintenance seems to make the assumption that all animals will participate in breeding, but often, it seems individuals just aren't interested. Is there a way to squeeze out gametes like they do with salmonids?

That only is a problem if you have a very small founder population. If you have 50 individuals, for example, from the founder population, you can easily manage the population and alleles within it. I believe that you can do so down to 12 or 13 individuals and still maintain a very high proportion of the representative genetics of the population.

Originally Posted by frogfarm

With the few atelopus that seem to prove resistant to chytrid, is it a genetic resistance? How is the wild allele frequency going to look between the cb and wild pops in 50 years when those few individuals left in the wild start a new population?

If the population is small enough, you're going to have a genetic bottleneck which can be just as bad for the population. As Ed said, it's largely dependent on the situation. How many are reintroduced depends on how many are in the wild. If there's nothing, the population can be totally resupplemented from a captive population. But if there is an existing population, it can be supplemented from a few individuals in the captive population. Enough to genetically rescue the population, but not enough to totally change the dynamic of the wild population.

Aren`t you assuming there is no catastrophic change going on that will change the population or environment to a point where the cb stock won`t be good for repatriation efforts? Isn`t that exactly WHY were holding on to wc genes because they (pops and the environment)are changing?

If a reintroduction program maintains the same genetics that the wild population had when the founder population was initially collected, then the captive bred frogs will have the same tools available to them to use as the wild frogs.

Plus this shifting pairs, isn`t that dangerous? If there happens to be the next chytrid getting into one animal, over the time it will be transferred to all just like any sexually transmitted disease.
By chytrid I mean any disease that animals can act as a carrier for.

Yes, it's a potential issue, as Ed had pointed out. In order to do a reintroduction program, there needs to be an overhaul on many aspects of keeping frogs, including biosecurity.

[Ed]

Originally Posted by spinycheek

What if you can't get every frog to pair up? Allele maintenance seems to make the assumption that all animals will participate in breeding, but often, it seems individuals just aren't interested. Is there a way to squeeze out gametes like they do with salmonids?

If necessary, yes. Hormonal induction of reproduction in anurans has been well studied and used in multiple species.

Ed

[spinycheek]

Nice! I always wondered if anyone had perfected using hormones to instigate breeding.

[Ed]

Originally Posted by frogfarm

With the few atelopus that seem to prove resistant to chytrid, is it a genetic resistance? How is the wild allele frequency going to look between the cb and wild pops in 50 years when those few individuals left in the wild start a new population? Aren`t you assuming there is no catastrophic change going on that will change the population or environment to a point where the cb stock won`t be good for repatriation efforts? Isn`t that exactly WHY were holding on to wc genes because they (pops and the environment)are changing?
Plus this shifting pairs, isn`t that dangerous? If there happens to be the next chytrid getting into one animal, over the time it will be transferred to all just like any sexually transmitted disease.
By chytrid I mean any disease that animals can act as a carrier for.

At this time, there isn't any indication that this is a genetic resistance as in some populations of other hard hit anurans in which there are adults with active infections, recruitment is below that needed to sustain the populations (in some cases it is zero). There are also different rates of mortality depending on the strain of chytrid infecting the individual animals (see http://www.int-res.com/articles/dao2005/68/d068p047.pdf for some examples). It is possible that they are infected with a less virulent or a avirulent strain. It is also possible that the adults in those populations have to date been able to manage the infection through behavioral changes (basking for example) keeping the chytrid out of the lethal temperature zone but in these cases, again recruitment tends to be below that needed to sustain the population.
Now I hope it is a genetic resistence to the fungal infection but I'm enough of a realist to understand that the odds are not in favor of genetic resistance.

As a further complication attempts to immunize anurans against chytrid have failed but this may be due to the fact that this is a relatively new field.

With respect to transmission between collections, basic quarantine procedures and testing would eliminate the risk. The risk isn't any different than adding a new frog to a collection and breeders and hobbyists are doing that all the time....

Ed

[Toby_H]

Originally Posted by Corpus Callosum

They don't offer the same results, that's exactly the point we are trying to make. In a conservation genetics when a captive population is managed in captivity we are not trying to mimic the selection pressures which exist in nature. We are just trying to retain as many of the original alleles as possible from the founder stock.

If the underlined sentence above is true, this is the misunderstanding that allowed the discrepancy…

“Managing allele frequency”, genetic “Snapshot” and genetic “Freeze” indicate keeping the same allele ratio as the wild population. In the quote above you suggest ‘Preserving Genetic Diversity’ not “Frequency”. It does not preserve the allele ratio of the wild stock, but does in fact preserve the diversity.


While I can see this as a valid approach when the goal is future reintroduction, I wish terminology would have been more accurate/clear to better express this much earlier in the conversation.


Michael, thank you very much for clarifying this detail… Skylsdale, my apologies for my line of questioning and the resultant debate derailing your thread. I only entered into it as it is an interesting topic and I hope flows further.