Patterns of genetic diversity in vervet monkeys (Chlorocebus aethiops) from the south eastern regions of South Africa

Abstract

Vervet monkeys (Chlorocebus aethiops) are one of the most widely distributed primate species in Africa. The aim of this study was to determine the level of genetic differentiation among conspecific vervet monkey populations in the south-eastern regions of South Africa, as part of a bigger project to determine levels of differentiation across South Africa. For this purpose, samples were taken from four localities in the Free State Province (Soetdoring Nature Reserve (NR), Gariep Dam NR, Sandveld NR and the Parys area), four Eastern Cape locations (Tsolwana NR, Baviaanskloof NR, Shamwari Private Game Reserve (PGR) and the Nelson Mandela Metropolitan University (NMMU) campus, Port Elizabeth), three Kwa-Zulu Natal location (St. Lucia area) and one Limpopo Province locality. Genetic differentiation was quantified using sequence data from a portion of the mtDNA control region. Twelve Haplotypes were identified within the total sample group. The nucleotide diversity for each grouping was calculated over all loci. Nucleotide diversity ranged from 0 to 0.038% ±0.02. Haplotype frequencies distribution among samples was calculated. An analysis of Molecular Variance (AMOVA) test was conducted and population pairwise FST values were estimated. The AMOVA test revealed that the majority of the genetic diversity occurred among the different groups (52.5%), with only 4.9% of the variation found within populations. The populations were assigned to groups according to geographic origins. The pairwise analysis identified significant levels of genetic variation among populations, with an average FST value of 0.851. These haplotypes were found to coincide with the geographical borders of Provinces. A ML tree was constructed using the haplotype data, and results showed clustering corresponding to geographical borders. A phylogenetic network was constructed, and this showed clustering similar to that found with the ML tree analysis. According to these results it is clear that there is genetic structuring among vervet monkey populations in South Africa. This clustering of populations can be potentially explained by female philopatry and geographical barriers. Female philopatry is a well known occurrence amongst Cercopithecine primates. The occurrence of geographical barriers, such as rivers and mountains had influence on migration rates and genetic structuring. This clustering pattern observed with mtDNA analysis contradicts results from previous studies working with nuclear DNA markers. This can be caused by various factors. Except for female philopatry having an effect on mtDNA differentiation patterns, it should be noted that the faster evolutionary rate of mtDNA vs. nuclear DNA can also cause different genetic patterns. The effective population size of mtDNA is also four-fold smaller than that of nuclear genes, and will also cause skewed results when comparing mtDNA data with nuclear DNA data. No reliable recommendations can be made toward the release of rehabilitated vervet monkeys, as further analysis is needed. It is thus suggested to use both genetic markers in follow-up studies. An increase in sample size from a broader geographical range is also recommended. In addition to further work on patterns of genetic variation, the adaptive significance of observed genetic differences should also be investigated.