Hunting pressure and the population genetic patterns and sex-mediated dispersal in the Guinea Baboon in Guinea-Bissau

Abstract

In Guinea-Bissau (GB) the Guinea baboon (Papio hamadryas papio) is threatened by hunting pressure. Along with local extinctions, these practices may be inducing long-term genetic changes and disrupting underlying social structure. In this study, the bushmeat trade in GB was evaluated for the first time and the effect of hunting practices on the genetic diversity and population structure was investigated. By following the bushmeat trade at urban markets, we found baboons to be the third most traded primate species. Male baboon carcasses were sold at a price 60% higher than any other primate due to their larger body mass. Semi-structured interviews conducted with hunters revealed a preference towards male baboons and recent difficulty in finding this primates species. Non-invasive DNA sampling in southern GB and two different genetic markers (fourteen microsatellite loci and a fragment of the mitochondrial control region) suggested substantial levels of genetic diversity and recent genetic contact between different populations. However, geographic distances had a weak effect on population structure and the genetic discontinuities found were not related with landscape features. A contact zone was identified. Here, gene flow seems to be unidirectional and admixed individuals were in higher proportion. Hunting pressure may have induced recent contact between genetically differentiated individuals, which now co-exist in the same social unit. Additionally, the sex-specific patterns of gene flow and the composition of social units were compared with a non-hunted Guinea baboon population, using a molecular sex determination protocol and thirteen microsatellite loci. GB displayed a lower ratio of males within social units, which are formed in some cases by unrelated individuals. The clear female-biased dispersal pattern displayed in Senegal was less intense in GB, where gene flow seems to be mediated through both sexes. The aforementioned contact zone resulted from male immigration. Male baboon dispersal in GB could be the result of flight behaviour or a consequence of an altered sex ratio induced by hunting practices. The GB baboons displayed signs of a disrupted population and its future conservation requires specific actions to reduce or eliminate this activity