Conservation genetics of bush mango from central/west Africa: implicationsfrom random amplified polymorphic DNA analysis

Genetic variation was assessed in the two bush mango species, Irvingia gabo nensis and I. wombolu, valuable multipurpose fruit trees from central and w est Africa that are currently undergoing domestication. A total of 130 indi viduals sampled from Cameroon, Nigeria and Gabon were analysed using 74 ran dom amplified polymorphic DNAs (RAPDs). Significant genetic integrity was f ound in the two morphologically similar species (among-species analysis of molecular variance [AMOVA] variance component 25.8%, P < 0.001), with no ev idence of hybridization, even between individuals from areas of sympatry wh ere hybridization was considered probable. Results suggest that large-scale transplantation of either species into new habitats will probably not lead to genetic introgression from or into the other species. Therefore, subseq uent cultivation of the two species should not be hindered by this consider ation, although further studies on the potential for hybridization/introgre ssion between these species would be prudent. Significant genetic different iation of both species (among-countries within species, nested AMOVA varian ce component 9.8%, P < 0.001) was observed over the sampled regions, and ge netic similarity of samples decreased significantly with increasing geograp hical distance, according to number of alleles in common (NAC) analysis. 'H ot spots' of genetic diversity were found clustered in southern Nigeria and southern Cameroon for I. wombolu, and in southern Nigeria, southern Camero on and central Gabon for I. gabonensis. The possible reasons for this distr ibution of genetic variation are discussed, but it may reflect evolutionary history, as these populations occur in areas of postulated Pleistocene ref ugia. The application of these results to domestication programmes and, in the light of extensive deforestation in the region, conservation approaches , is discussed.