The geographic distribution of genetic diversity within gorillas.

Gorillas, like all non-human great apes, are endangered. Understanding the distribution of genetic diversity across their range is important because low diversity may arise in small populations through increased inbreeding, and, by reducing reproductive fitness, may lead to decreased chances of persistence of a given population. Previous studies found higher genetic diversity in the western (Gorilla gorilla) than in the eastern gorillas (Gorilla beringei), but rarely employed individuals of known geographic origin to investigate the distribution of diversity across multiple populations. The present study fills that gap by analyzing 1,161 individuals from nine sites across all four currently recognized Gorilla subspecies. Genetic diversity at each site was estimated using published data from seven highly-variable microsatellite loci. We found that the small and fragmented populations of Cross River gorillas, eastern lowland gorillas and mountain gorillas were less diverse than any of the five analyzed western lowland gorilla populations. The higher levels of genetic variation within the western lowland gorillas might be best explained by the facts that they (i) exhibit larger present and past effective population sizes than the other subspecies and (ii) maintain higher rates of gene flow through the existence of largely continuous habitat within their range. With regard to conservation, the high genetic diversity within western lowland gorillas is encouraging and retention of dispersal corridors between already protected areas is essential. Am. J. Primatol. 77:974-985, 2015.