inbred

Not only that, but the pupfish are believed to be one of the most inbred of all species, a lack of genetic variation that makes it difficult for the creatures to procreate and thrive.

In bees, males are typically haploid and have only one set of chromosomes, but when they're inbred, they can have two sets of the same chromosomes and lack genetic diversity.

Where possible, farmers use hybrid varieties, which are created by crossing two inbred lines and are more resistant and higher-yielding than normal varieties.

More recently, studies have found the southern resident females have less hunting success than their neighbors up north and that the shrinking, increasingly inbred population of southern residents could be plummeting toward extinction.

Bowie noted that the results bear on a major debate in conservation biology today -- whether it is wise to bolster small, threatened, inbred populations by breeding them with related populations.