If you have a low population of an endangered species, how do you get the numbers up without inbreeding or ‘diluting’ the original species?

Question

I’m talking the likely less than 50 individuals critically endangered, I’d imagine in 50-100 groups there’s possibly enough separate family groups to avoid inter-breeding, it’s just a matter of keeping them safe and healthy.

Would breeding with another member of the same family group* potentially end up changing the original species further down the line, or would that not matter as you got more members of the original able to breed with each other? (So you’d have an offspring of original parents, mate with a hybrid offspring, their offspring being closer to original than doner?)

I thought of this again last night seeing the Sumatran rhino, which is pretty distinct from the other rhinos.

Edit: realised I may have worded a part wrongly. *genus is what I meant not biologically related family group. Like a Bengal Tiger with a Siberian Tiger. Genetically very similar but still distinct.

In: Biology

Answer 1

There’s the rule (of thumb) of 500, and the rule of 5,000. Generally speaking, a population with 5,000 members can breed back up to sustainable numbers with out any significant issues. With 500, it can breed to sustainable numbers, but there will be significant genetic difference from the original population. Which can be the inbreeding issues you mentioned.

But it’s still better for the health of a species to exist with inbreeding issues than to not exist at all.