Name: Teixeira H

Biodeserts supervisors: Silva MJF, Brito JC

Title: Landscape genetics of Guinea baboon: assessing population structure, gene flow dynamics, and functional connectivity with molecular and spatial tools

Institution: University of Porto

Status: Completed

Abstract

Habitat fragmentation represents one of the greatest threats to biodiversity worldwide. Although it can be the result of natural events, human activities are largely responsible for the transformation of landscapes into heterogeneous matrixes containing mosaics of suitable and unsuitable habitats. As a consequence of fragmentation, populations may become small and isolated and, ultimately, genetically impoverished. Genetic diversity is crucial for the long-term persistence of a species and the basis for species’ adaptability to potential environmental changes. Maintaining gene flow between populations may avert genetic erosion, preventing reproductive isolation and the fixation or loss of alleles and accumulation of deleterious mutations. Therefore, the persistence of animal species in fragmented landscapes is related with the animals’ ability to disperse across heterogeneous landscapes and the occurrence of functional connectivity among isolated patches. Landscape genetics provides a direct way of determining functional connectivity. The Guinea baboon (Papio papio) is a well-adapted primate species distributed across a wide range of habitats in West Africa, including mountains, woodlands, humid high forests, and mangrove forests. Human activities, such as habitat conversion, deforestation and hunting, significantly reduced the distribution of Guinea baboons and increased fragmentation during the last 30 years. In this study, genetic data of 507 Guinea baboon individuals collected in 10 populations across West Africa were combined with spatial analyses to investigate the most suitable areas of dispersal and the isolation mechanisms related to its genetic structure. The individuals were genotyped for a maximum of 23 autosomal microsatellites loci. A variable Y-linked microsatellite marker was investigated by testing a set of 15 markers previously developed for humans. Two ecological niche-based models were generated to separately compare the impacts of environmental factors and human-related features on the distribution. The electrical circuit theory was used to predict the functional connectivity and simple and partial Mantel tests were used to evaluate hypotheses of isolation by distance and isolation by resistance. Of the 15 Y-linked microsatellites loci tested, only one was polymorphic, suggesting low levels of polymorphism associated with the Y chromosome in the Guinea baboon. Genetic analyses suggested major differences between the populations located in the northern, eastern and western extremes of the distribution. Ecological models predicted the existence of suitable areas outside the known distribution of Guinea baboon, indicating that the IUCN distribution area should be updated. The population located in the south-eastern distribution of the species likely represents the hybridization zone between Guinea and Olive baboons. The spatial analyses suggested that the isolation by distance hypothesis was the most probable explanation for the observed genetic structure in Guinea baboon. The landscape features that could act as barriers to gene flow did not fully related with the genetic discontinuities found, which emphasizes the plasticity and ability of Guinea baboons to adapt to heterogeneous and fragmented landscapes. In the future, extensive efforts may be required to find a variable Y-chromosomal marker for Guinea baboon. Samples from currently unsampled areas are needed to detail genetic diversity and functional connectivity across the full species range. Further studies are needed to confirm the occurrence of hybridization between Guinea baboon and Olive baboon in the south-eastern distribution of Guinea baboon.