The cryptic genetic structure of the North American captive gorilla population

Western lowland gorillas (Gorilla gorilla gorilla) were imported from across their geographical range to North American zoos from the late 1800s through 1974. The majority of these gorillas were imported with little or no information regarding their original provenance and no information on their genetic relatedness. Here, we analyze 32 microsatellite loci in 144 individuals using a Bayesian clustering method to delineate clusters of individuals among a sample of founders of the captive North American zoo gorilla collection. We infer that the majority of North American zoo founders sampled are distributed into two distinct clusters, and that some individuals are of admixed ancestry. This new information regarding the existence of ancestral genetic population structure in the North American zoo population lays the groundwork for enhanced efforts to conserve the evolutionary units of the western lowland gorilla gene pool. Our data also show that the genetic diversity estimates in the founder population were comparable to those in wild gorilla populations (Mondika and Cross River), and that pairwise relatedness among the founders is no different from that expected for a random mating population. However, the relatively high level of relatedness (R = 0.54) we discovered in a pair of known breeding pairs reveals the need for incorporating genetic relatedness estimates in the captive management of western lowland gorillas.