Abstract:
Adansonia digitata and Vitelleria paradoxa are multi-purpose forest tree species which provide a range of forest products and play vital role in the rural economy. These tree species are increasingly scarce due to deforestation and forest degradation. These have been affecting the reproductive potentials of the species and threatened their continuous availability. The mating system of A. digitata and V. paradoxa have been limited to studies of their reproductive biology. This study investigated the socio-economic importance, genetic diversity and mating system of Adansonia digitata and Vitelleria paradoxa in three agro-ecological zones (Derived savanna, Guinea savanna and Sudan savanna) of Nigeria. From each agro-ecological zones, locations with high number of A. digitata and V. paradoxa species were purposively selected. Ten communities were purposively selected in each agro-ecological zone. Two sets of semi-structured questionnaires (household and key informant) were used to gather information from 330 respondents. The fidelity levels of different plant parts of both A. digitata and V. paradoxa were estimated. Associations between variables were carried out using Chi-square. Two (2) juvenile leaves were collected from fifteen sub population of A. digitata and V. paradoxa. The leaves were cleaned and preserved with silica gel in sealed nylon. Seeds of A. digitata and V. paradoxa were also collected for mating system analysis. Ten microsatellite molecular markers were used in the analysis of their genetic similarities. Findings from this research revealed that A. digitata and V. paradoxa help to increase the household income. Result shows there was no significant association (P≤0.05) between communities and income from the sales of A. digitata and V. paradoxa during the rainy season. With respect to the different plant parts, the leaves and the seed of A. digitata and V. paradoxa showed a high fidelity level (95% and 92%). This research revealed high genetic variation within populations of A. digitata and V. paradoxa, and low genetic variation among populations of A. digitata and V. paradoxa. Heterozygosity levels differed between the two studied life stages, suggesting that selection against homozygotes occur during the plant life cycle. The mating system parameters analyzed indicate that A. digitata and V. paradoxa were predominantly outcrossed. However, their low levels of selfing rate suggest that there was individual variation with regard to self-incompatibility, which can be a survival strategy in isolated or fragmented habitats. Biparental inbreeding was discovered in the two species and their progenies were predominantly full-sibs. It was discovered that A. digitata and V. paradoxa are important economic trees in savanna (Derived, Guinea and Sudan) ecological zones of Nigeria and contribute to the socio-economic life of the people. Therefore, effort should be made to conserve and ensure the long time survival of the remaining A. digitata and V. paradoxa species in Nigeria.
