Genetic diversity and population structure of a threatened tree species Afzelia africana Sm. ex Pers. among climatic zones for conservation challenges in Benin (West Africa)

Afzelia africana Sm. ex Pers. is an African endangered tree species whose natural populations are declining severely because of human pressure through logging, fodder, and fuel harvesting. Despite the importance of molecular ecology in these decades, no information regarding population genetics is available to motivate the conservation of this tree species in Benin. This study was then carried out to assess the genetic diversity and population structure of A. afrcana from different zones by SSR markers analysis to infer conservation implications. Two hundred sixty-four split into twenty-six populations were sampled in the three climatic zones and genotyped at 11 SSR loci measuring genetic diversity and population structure analysis. High levels of genetic diversity were found over the three zones. Mean values of observed/expected heterozygosities ranged from 0.81 to 0.88 and from 0.75 to 0.77, respectively. The pattern of population structure revealed by SSR loci indicated three gene pools in North-West, North-East, and South Benin. The population of the Sudano-Guinean zone exchanges gene with the other zones. We observed a weak but statistically significant genetic differentiation among geographical zones regarding the values of Fst (Value = 0.028; p = 0.001). Significant isolation by distance was obtained with the Mantel test. The observed pattern of population and genetic diversity by SSR loci offers useful insights to guide sustainable management and conservation decision of A. africana populations in different climatic zones of Benin.