International Journal of Molecular Evolution and Biodiversity 2024, Vol.14, No.3, 108-119 http://ecoevopublisher.com/index.php/ijmeb 110 increasing the risk of inbreeding. For instance, the extensive inbreeding observed in eastern gorillas is likely a consequence of habitat fragmentation and reduced population sizes. Gene flow, on the other hand, can introduce new genetic variants into a population, enhancing genetic diversity and adaptive potential. The genetic distinctiveness of chimpanzee populations, for example, is partly due to historical gene flow events that have shaped their current genetic structure. 3 Population Structure in Primates 3.1 Geographical patterns of genetic structure Geographical patterns of genetic structure in primates are influenced by various factors, including historical migrations, environmental barriers, and social behaviors. Studies have shown that genetic diversity and differentiation can vary significantly across different geographic regions. For instance, In gorillas, nucleotide diversity studies have shown that western lowland gorillas possess the highest levels of genetic diversity among African apes, which is about twice that of humans (Yu et al., 2004). This high diversity is indicative of substantial historical population sizes and migrations. In baboons, genome sequencing of six species has revealed multiple episodes of admixture and introgression, highlighting the complex evolutionary history and geographic structuring within the genus Papio (Figure 1) (Rogers et al., 2019). Figure 1 Papio baboon species (Adopted from Rogers et al., 2019) Image caption: (A) The appearance and current distribution of each baboon species, and the locations of three well-documented active hybrid zones are also shown. x1: hybrid zone between P. hamadryas and P. anubis (Phillips-Conroy et al., 1991; Bergman et al., 2008); x2: hybrid zone between P. cynocephalus and P. anubis (Tung et al., 2008; Charpentier et al., 2012); x3: hybrid zone between P. kindae and P. ursinus (Jolly et al., 2011); Drawings of each species by S. Nash. (B) Distinguishing features of Papio species (Adopted from Rogers et al., 2019) 3.2 Social structure and genetic differentiation Social organization plays a crucial role in shaping the genetic structure of primate populations. In species where males are the dispersing sex, such as baboons, social structure and behavior can predict molecular genetic measures of relatedness and reproductive success. For example, in Guinea baboons, female-biased gene flow has been observed, contrasting with the male-biased dispersal seen in other baboon species. This unique social system results in a lack of genetic-geographic structuring and higher genetic variation within demes (Kopp et al., 2013). 3.3 Historical demography Reconstructing the historical demography of primates involves analyzing genetic data to infer past population sizes and migration events. For instance, studies on baboons have utilized ancient DNA to demonstrate long-term population continuity in southern Africa, providing insights into the demographic history of the species (Mathieson et al., 2020). Similarly, nucleotide diversity analyses in gorillas have been used to estimate long-term effective population sizes, shedding light on their historical population dynamics (Yu et al., 2004).
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