|
Richard A. Bergl1,2 and Linda Vigilant3 1Anthropology Program, City University of New York Graduate Center, 2New York Consortium in Evolutionary Primatology (NYCEP), 3Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Germany Abstract Cross River gorillas (Gorilla gorilla diehli) total approximately 300 individuals in at least ten localities which are divided into three subpopulations. In small and fragmented populations such as this, genetic diversity may be reduced, as variability will be lost faster due to increased levels of drift and inbreeding. This reduced diversity is of concern for conservationists as it is often associated with decreased fitness and a higher threat of extinction. However, it is difficult to determine when a population has low diversity except in a comparative context. We assessed genetic variability in the critically endangered Cross River gorilla using a suite of 11 autosomal microsatellite loci. First we examined patterns of diversity within the Cross River population. We show that levels of diversity are not evenly distributed across subpopulations, and that one subpopulation has higher levels of variability than the others. Second, we compared levels of diversity in the Cross River gorillas to three other gorilla populations for which published data were available. All measures of genetic variability in the Cross River population were comparable to those of the similarly small mountain gorilla (Gorilla beringei beringei) populations (Bwindi and Karisoke). However, for some measures both the Cross River and mountain gorilla populations show lower levels diversity than a sample from a large, continuous population (Mondika, Gorilla gorilla gorilla). Finally, we tested for the genetic signature of a bottleneck in each of the four populations. Though Bwindi, Karisoke and Cross River are all small populations, only Cross River showed strong evidence of a reduction in population size. The evidence for a bottleneck in the Cross River gorilla population suggests that reduction in the size of this population was more recent or abrupt than in the two mountain gorilla populations. |