Name: Gerini F

Biodeserts supervisors: Ferreira Silva, MJ

Co-supervisors: Sergio Tofanelli (University of Pisa)

Title: Comparative population genetic structure of the Western Chimpanzee and Guinea baboons of Guinea Bissau, West Africa

Institution: University of Pisa, Italy

Status: Completed




Investigating patterns of gene flow across the same landscape for primates with different socio-ecological requirements can improve the ability to identify barriers to dispersal (e.g. rivers, villages) or the landscape features facilitating gene flow (e.g. ecological corridors). Such information is important to draw-up conservation plans to maintain genetic exchange among sub-populations in the long-term. We investigated the genetic diversity, population structure and gene flow of two co-distributed primates - Pan troglodytes verus (the Western chimpanzee) and Papio papio (the Guinean baboon), that are both threatened by hunting and habitat loss in a human-dominated landscape in southern Guinea-Bissau. Previous studies on Western chimpanzees and Guinea baboon found indications of disrupted dispersal in GB and a weak population structure, we decided to deepen the subject increasing the number of loci for P. t. verus (from 11 to 22) and including the protected area further east of the country (Boé NP) little represented in previous studies. We also included a new protected area for baboons (Dulombi NP).
We aimed i) to describe genetic diversity and population structure of the two species given the inclusion of new areas and verify whether the increase in loci has enhanced the discriminatory power for Pan troglodytes verus; ii) to assess patterns of gene flow (directionality and magnitude) across protected areas for each species and compare the patterns between species in order to identify possible barriers or preferential flow-ways; iii) to verify if the two species present a female driven dispersion as known in the literature or whether further tests confirm the perturbation of the sex-biased dispersal and iv) to infer the chance of long-term survival for the two species through the estimation of effective population size and detection of recent demographic bottlenecks.
We collected 299 samples in Boé National Park. Samples were genotyped using between 14 to 21 autosomal microsatellite loci. The sex of the individuals was determined using molecular protocols. Genotypes were merged into previously generated datasets. The final genetic dataset under analysis included 105 P. t. verus samples and 126 Papio papio from three protected areas (Cufada Lagoons, Dulombi NP and Boè NP).
The three populations are not significantly distinct in terms of genetic diversity estimated for both species. Results from individual-based Bayesian clustering confirm a weak population structure in Pan troglodytes verus and in Papio papio and suggest that Boé NP population is a genetically distinct unit for both species. The Corubal river does not seem to constitute a significant barrier to gene flow for both species. The population of Guinea baboon show signs of a demographic bottleneck. Dispersal in Pan troglodytes verus and Papio papio seems to be mediated by both sexes in GB, which constitute an exception from what is known in the literature and it could be due to anthropogenic disturbances. Our findings should be considered by governmental agencies when managing the network of protected areas. Law enforcement should be improved along the ecologic corridors between the protected areas as these are important dispersing routes.