Abstract
Vervet monkeys (Chlorocebus pygerythrus) are one of the most widely distributed non-human primate species found in South Africa. They occur across all the South African provinces, inhabiting a large variety of habitats. These habitats vary sufficiently that it can be assumed that various factors such as pathogen diversity could influence populations in different ways. In turn, these factors could lead to varied levels of selection at specific fitness linked loci. The Toll-like receptor (TLR) gene family, which play an integral role in vertebrate innate immunity, is a group of fitness linked loci which has been the focus of much research. In this study, we assessed the level of genetic variation at partial sequences of two TLR loci (TLR4 and 7) and a reproductively linked gene, acrosin (ACR), across the different habitat types within the vervet monkey distribution range. Gene variation and selection estimates were also made among 11–21 primate species. Low levels of genetic variation for all three gene regions were observed within vervet monkeys, with only two polymorphic sites identified for TLR4, three sites for TLR7 and one site for ACR. TLR7 variation was positively correlated with high mean annual rainfall, which was linked to increased pathogen abundance. The observed genetic variation at TLR4 might have been influenced by numerous factors including pathogens and climatic conditions. The ACR exonic regions showed no variation in vervet monkeys, which could point to the occurrence of a selective sweep. The TLR4 and TLR7 results for the among primate analyses was mostly in line with previous studies, indicating a higher rate of evolution for TLR4. Within primates, ACR coding regions also showed signs of positive selection, which was congruent with previous reports on mammals. Important additional information to the already existing vervet monkey knowledge base was gained from this study, which can guide future research projects on this highly researched taxon as well as help conservation agencies with future management planning involving possible translocations of this species.
Highlights
Data on the level of genetic adaptation within animal populations is an important aspect of conservation biology
A moderate amount of genetic diversity was observed for the two Toll-like receptor (TLR) exonic gene regions, with only one polymorphic site observed within the intronic region of the vervet ACR gene region (SNP frequencies: T/T = 0.76; T/G = 0.2; G/G = 0.04)
For the TLR gene regions we observed two polymorphic sites for TLR4, with one non-synonymous position identified in the vervet population from the C2 region, and three polymorphic sites for TLR7, with one non-synonymous position observed in vervet populations from the N1, NC1 and NC2&3 regions
Summary
Data on the level of genetic adaptation within animal populations is an important aspect of conservation biology. Population or habitat specific adaptations should be considered when studying animal population dynamics and evolution, as these aspects of population genetic diversity will undoubtedly provide important information to guide conservation management (Funk et al, 2012). Vervet monkeys (Chlorocebus pygerythrus) are one of the most widely distributed nonhuman primate species found in South Africa, with only Papio ursinus found in a wider range (Hoffmann & Hilton-Taylor, 2008). This species occurs across all the South African provinces, inhabiting a large variety of habitats (Skinner & Chimimba, 2005; Kingdon et al, 2008), including xeric and mesic zones. Further research into the adaptive genetic diversity of vervet monkeys will be of value for future studies on this widely researched taxon but can provide
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