When there’s a nearly-extinct species with only one male or one female left, how are genetic defects from inbreeding dealt with?

Question

Inbreeding, along with being widely considered immoral, also causes genetic defects in its offspring from the undiversified gene pool. When a species is brought back from the brink because there is one remaining known couple capable of mating with one another, how does the species deal with the first few generations?

In: Biology

Answer 1

does that happen? There is a concept of “functionally extinct” in which there are too few individuals left to viably regenerate the population.

Answer 2

That doesn’t really happen. But in general, when genetic diversity is extremely low the best conservation biologists can currently do is just to mix around what little variation there is, bringing individuals from one isolated population to another to get as much diversity as possible.

Answer 3

Inbreeding doesn’t “cause” genetic defects, per se. It increases the chance that negative recessive traits will be exhibited in the offspring. The key point being the parents have to each have a copy of the negative allele. That’s the main risk of inbreeding. However, it is entirely possible (and common in many instances) for inbred species to be well adapted to their environment and not exhibit any particular negative traits. Much of our agriculture is like this, for example. It’s a pop culture myth that inbreeding always results in inferior offspring. It can, but it doesn’t necessarily have to. And any inferior offspring were also possible (although less likely) from pairing of more diverse individuals.

The other issue is that a lower genetic diversity makes the species more susceptible to a change in environment.

Answer 4

There’s not much that can be done. It can have an effect. I know that recently on Isle Royale the wolf population became very inbred and had defects. [https://www.eurekalert.org/pub_releases/2019-05/mtu-goi052419.php](https://www.eurekalert.org/pub_releases/2019-05/mtu-goi052419.php)

I believe that wolf population no longer exists today.

One thing that can happen when a species almost goes extinct and comes back is referred to as a genetic bottleneck. Since all members of the population will be really closely related, a pressure that effects one of them will likely effect all of them. That lack of biodiversity puts the entire population at risk of pressures that an older more diverse population would have a better chance at surviving.

Basically it’s luck that nothing happens though.