Evolutionary history of the tropical fruit tree species Dacryodes edulis : conservation and sustainable management implications

Abstract

In tropical forest ecosystems, humans have always benefited from useful plant species, whether as a source of food, fiber, fuel, or medicine. Among these forest products, some of them have been progressively cultivated. This is the case of the African plum tree (Dacryodes edulis, Burseraceae), an emblematic fruit tree of Central Africa. This PhD thesis addresses different aspects of the dynamics of the cultivated diversity of African plum trees via an interdisciplinary approach using population genetics and ethnoecology. The first part focuses on the evolutionary history of African plum tree; the second on the cultivation and management practices of the species by different ethnic groups in Cameroon. The third part, bringing together the two disciplines, aims to understand the influence of these different practices on the genetic diversity of the species.Over its distribution area, the genetic diversity of African plum trees is structured into three main groups. Geographically, the most extensive, which also presents an internal substructure, covers populations of Cameroon and North Gabon. The other two are located at its range margins, in Nigeria and the Democratic Republic of Congo. A historical barrier is suggested on either side of the meteorological equator. These patterns of intra-specific genetic diversity distribution might reflect the impact of Quaternary glaciation events rather than the one of species cultivation. Finally, the sharing of haplotypes between D. edulis and other sympatric congeneric species suggests that inter-specific gene flow can occur.An ethnoecological approach in different African plum production areas in West Cameroon has shown that greater integration into the plum market results in more diversified planting practices and does not have a deleterious effect on varietal diversity in the field. This morphological diversity is also supported by a rich vernacular nomenclature, counting more names for Beti than for Bamileke a