Noninvasive analysis of population genetic structure of Mountain Gorillas (Gorilla beringei berigei) of Bwindi National Park in Uganda

Abstract

Several studies on mountain gorillas have focused on behavior and the recent census. Very little is known about the genetic structure that exists in this endangered species despite the numerous intervention measures being put to try and save the rapidly reducing numbers as a result of poaching, habitat destruction and population pressure on the same resources. In this study, data analyzed from 98 feacal samples collected from Bwindi Impenetrable and Mgahinga National Park at 13 highly polymorphic tetra-nucleotide loci were used to infer the population structure of mountain gorillas. Genetic diversity was measured in terms of number of alleles, observed and expected heterozygosity. Population structure was defined by comparing the genetic diversity within and between different groups and the number of migrants between groups and population clusters. Two clusters were computed based on the altitudinal home ranges of the gorillas with the Mgahinga group clustering with high altitude groups in Bwindi. Despite the two hierarchical genetic clusters, six significantly differentiated genetic groups were computed evidenced by the FST results, AMOVA and the unrooted genetic tree. Samples collected from Mgahinga were genetically different from those collected in Bwindi. Likewise there was much differentiation among the low altitude gorillas compared to the high altitude gorilla groups. Six private alleles were observed in four different populations (Shonji, Kyaguliro, Habinyanja and the Mgahinga population) at four loci in some cases with high frequencies of up to 0.58. Inspite of a migration rate of 1.24 migrants per generation, the relatively low levels of heterozygosity coupled with the high levels of genetic differentiation and high frequencies of private alleles implicate genetic drift as the major driving force shaping the genetic structure of these gorilla groups. The future survival of mountain gorillas is threatened by habitat fragmentation due to human activities and the rapid spread of zoonotic diseases. Therefore conservation efforts should by geared towards mitigating this trend.