Name: Borges F

Biodeserts supervisors: Silva MJF

Title: A country-level genetic survey of the IUCN critically endangered western chimpanzee (Pan troglodytes verus) in Guinea-Bissau

Institution: University of Porto

Status: Completed




Guinea-Bissau is considered one of the most important areas for the global conservation of the IUCN critically endangered western chimpanzee (Pan troglodytes verus). Rapid deforestation, habitat fragmentation, and hunting for pet trade threaten this subspecies in the country, which is further augmented by an atmosphere of political instability and a low level of human development. The lack of baseline information was hindering the development of a complete assessment of the viability and conservation status of P. t. verus.
The present study used 665 non-invasively collected faecal samples from five different geographic populations in Guinea-Bissau and a fragment of the mitochondrial DNA control region, a set of 21 autosomal microsatellite markers, and one Y-chromosome-associated microsatellite locus to assess genetic diversity and population structure, and to examine signatures of recent demographic history. A total of 185 unique genotypes and 165 mitochondrial DNA sequences were obtained and used in the analyses.
The results for all types of genetic markers suggested that gene flow between the chimpanzee population inhabiting Boé National Park and the coastal areas of Guinea-Bissau is limited. This result is in accordance to what had been found for the populations of baboons in the country. To assure this population does not go extinct, it is essential to recover the ecological corridors linking it to the southern part of Guinea-Bissau.
The patterns of population structure unravelled across the country were not strong, which suggests chimpanzees tend to disperse across almost all of their range. Contrary to what had been previously found for the majority of chimpanzee populations, males do not seem to be strictly philopatric in Guinea-Bissau. Evidences of population subdivision within Guinea-Bissau have been found based on the mitochondrial DNA marker, which is in agreement to the evolutionary history of the western chimpanzee clade.
A fine-scale analysis has been conducted to assess whether there is gene flow between the chimpanzee populations at Cufada Lagoons Natural Park and at Dulombi National Park. Dispersal between these populations seems to follow a pattern of isolation by distance, although the Corubal River, which is located between them, probably constitutes a relevant barrier to dispersal. This analysis showed a relatively high degree of genetic variation within Cufada, which may occur due to the presence of immigrants in the population.
The results of this study suggest that human-related barriers to dispersal, such as roads and villages, may be negatively impacting chimpanzees’ dispersal across the country. The subtle degree of genetic structure found at a broad scale, along with the patterns unravelled at the fine-scale analysis, suggests that local-scale studies may be used as a powerful method to detect potential barriers to dispersal at an early stage, which may help plan management actions more efficiently.
The present research constituted the most complete genetic survey of chimpanzees in Guinea-Bissau to date and highlighted the need to enhance law enforcement and to work alongside local communities to improve chimpanzee conservation in the future.