sinesalvatorem:

dhominis:

sinesalvatorem:

fermatas-theorem:

trichofishomania:

aquaristlifeforme:

Zoos prevent extinction. This is why I support zoos. This is why the world should support zoos.

Meme credit goes to the zookeepers at

www.facebook.com/ZoosSavingSpecies

@zoossavingspecies

Good zoos save species!!!

I want us to have actually saved these species, but I notice I’m confused about.  Aren’t most of these numbers below a healthy gene pool size? Basically, aren’t they all going to have major problems due to inbreeding and eventually die out because of it?

Please tell me how this works.

They’re probably going to be unusually susceptible to being wiped out by something, and will likely be weaker than if they had more genetic diversity, but I don’t think they’re likely to just die out from their own inbreeding unless the original founder population was already sick. IIRC, Australian dingos are so closely related that the founding population was probably smaller than that of the species mentioned above, because getting dogs to Australia is hard.

However, I am Not A Biology. Like, really really not. Someone with a better understanding of genetics and founder effects should definitely let me know if I have this all wrong.

First of all, the minimum population sizes they’re citing are *in the wild*. For a few of these, the population in the wild was unsustainably low, but there was a large enough captive population that genetic diversity could be maintained.

(Why don’t we count wild and captive populations together? Among other reasons, there are some few species that are totally extinct in the wild and aren’t likely to be reintroduced any time soon. We have over a hundred Hawaiian crows in captivity, but every time we try to reintroduce them their natural predator–the Hawaiian hawk–kills them. Apparently they defended themselves against hawks by mobbing them, but that’s a learned behavior and there are no Hawaiian crows alive that were taught it. Last I heard, researchers were trying to teach the crows that behavior. Not sure how that’s been going…)

@sinesalvatorem is absolutely right about low genetic diversity being an issue, though. If all the individuals in a population are genetically similar, you’re going to have issues with individuals getting two copies of recessive deleterious mutations, all individuals being similarly susceptible to a strain of infectious disease… fun stuff.

There’s a lot of active management–when numbers get that low, we tend to keep a very close eye on any genetic disease-appearing things, and then try to prevent that. The prairie chickens in Wisconsin, for example. There isn’t enough contiguous prairie land left in WI to sustain a big enough prairie chicken population, so conservationists have to transfer specific birds between populations for mating. (Sounds like a fun job.) Or, I’d assume, whatever strategies (ethical) dog breeders use to reduce genetic disease in really inbred populations.

Even when there’s a bottleneck, the effects might not be disastrous. The northern elephant seal was seriously overhunted until the late 1800s. At one point, there might’ve been fewer than fifty left, and because of their social structure/mating habits the effective population size (i.e. the number of individuals that actually contribute genetic material) may have been substantially lower. After hunting them was prohibited (and that was, at least at first, the only intervention), the population size increased pretty quickly. By the 1970s there were tens of thousands of individuals. I think it’s over a hundred thousand now, but don’t cite me on that.

Compared to the southern elephant seal, a closely related species that wasn’t hunted nearly to extinction, their genetic diversity is way down. But they seem to be doing fine–the population got to a stable level within a few decades (pretty good for a slowly reproducing species!), and it looks like it’ll stay stable as long as we don’t start hunting them again and climate change doesn’t affect them too much.

Some of these species will require an indefinitely long period of observation/management to maintain stable population sizes. Others will go extinct anyway, whether because of the effects of inbreeding or because their original ecosystem has changed so much that their niche is now absent or better filled by some other species. But a small population size isn’t necessarily a death sentence. (Extinction sentence?)

TL;DR there may be few or no individuals in the wild but a pretty good number in captivity; active management helps to ameliorate the effects of inbreeding; even significant inbreeding doesn’t necessarily lead to extinction.

Yay, thank you! This is very much what I wanted to know. @fermatas-theorem, if this is also what you wanted to know.