Conservation Genetics of Baobab (Adansonia digitata L.) in the Parklands Agroforestry Systems of Benin (West Africa)

Abstract

The present study occurred in the three climatic zones of Benin (6°25 - 12° N) and aimed at investigating the level of morphometric and genetic variation and spatial genetic structure within and between threatened baobab populations. A total of 137 individuals from six populations were analysed using morphometric data as well as molecular marker data generated with the AFLP technique. Five primer pairs resulted in a total of 217 scored bands with 78.34% of them being polymorphic. A two-level AMOVA revealed 82.37% of the total variation within populations and 17.63% among populations (P<0.001). Analysis of population structure with allele-frequency based F-statistics revealed a global FST of 0.127±0.072 (P<0.001). The mean gene diversity within populations (Hw) and the average gene diversity among populations (Hb) were estimated at 0.309±0.000 and 0.045±0.072, respectively. Baobabs in the Sudanian and Sudan-Guinean zones of Benin were short and produced the highest yields of pulp, seeds and kernels in contrast to the ones in the Guinean zone. The molecular results indicate some degree of physical isolation of the populations collected in the different climatic zones. We also found morphological differences but further analysis must be done to establish their origin which is certainly an interaction between genotype and environment. Sampling options of the natural populations are suggested for in or ex situ conservation.