Why is lack of genetic diversity bad

Unexpectedly, they found that IUCN's criteria were not closely linked to genetic diversity. The team developed an approach to estimate how fast a population is losing genetic diversity. They then tested their approach by mining the genetic database for species with two separate estimates of genetic diversity, using one estimate to calculate their statistic and the other as an independent measure.

The values were correlated. Fish and Wildlife and state programs to identify species of conservation concern, DeWoody said. The paper is forthcoming in the November issue of Biological Conservation.

Writer: Natalie van Hoose, , nvanhoos purdue. Sources: Janna Willoughby, , willoughby purdue. Andrew DeWoody, , dewoody purdue. The reduction of genetic diversity in threatened vertebrates and new recommendations regarding IUCN conservation rankings. Janna R. Willoughby 1; Mekala Sundaram 1; Bhagya K. Wijayawardena 2; Steven J. Kimble 1; Yanzhu Ji 1; Nadia B. Fernandez 1, 2; Jennifer D. Antonides 1; Maureen C. Lamb 2; Nicholas J. Large populations tend to have high genetic diversity many differences among individuals , while small populations lose much of this diversity, resulting in individuals that are more genetically similar to one another.

The sea otter's low level of genetic diversity is similar to endangered species, such as the cheetah and Tasmanian devil, said lead author Annabel Beichman, a UCLA graduate student in ecology and evolutionary biology.

She and her colleagues reconstructed the otter's evolutionary history and assessed its level of genetic diversity, history of changes in its population size, and levels of potentially harmful genetic variation. The biologists found evidence of potentially harmful genetic variation and of mating between closely related ancestors in the sea otter genome -- a pattern that is common in endangered species with small population sizes. The team analyzed the genome of Gidget, a female sea otter from the Monterey Bay Aquarium who died this year, as well as the genome of a South American giant otter as an evolutionary point of comparison.

There are 13 species of otters, and the sea otter and giant otter live in starkly different environments -- the giant otter in a warm freshwater environment and the sea otter in the frigid coastal waters of the North Pacific Ocean.

This study is the first comprehensive genomic analysis of otters. We should make sure to not let their population decline again. Beichman compares the sea otter's low genetic diversity to a jar of multicolored marbles that has lost many of its colors. But if you've lost all your green marbles by chance when the population declined, you may be stuck with only blue and red -- and not able to resist the disease," she said. While seals and sea lions have lived in the ocean for 30 million years, and whales and dolphins for more than 50 million years, sea otters have had only about 5 million years to adapt to their marine environment.

Whales, seals, sea lions and dolphins have a blubbery layer of fat to keep them warm in their environment of cold saltwater, but sea otters lack that layer.

Instead, they have dense and water-repellant fur. Sea otters were hunted since the mids for their fur, almost to extinction. But if they do not exist — if the right genetic variation is not present — the population will not evolve and could be wiped out by the disease.

As an endangered species dwindles, it loses genetic variation — and even if the species rebounds, its level of genetic variation will not. Genetic variation will only slowly be restored through the accumulation of mutations over many generations. For this reason, an endangered species with low genetic variation may risk extinction long after its population size has recovered.

The risk of extinction or population decline because of low genetic variation is predicted by evolutionary theory. Scientists have not yet found any absolutely clear-cut examples of this in endangered species today, but they continue to investigate the possibility.