Genetic consequences of anthropogenic disturbances and population fragmentation in <Emphasis Type="Italic">Acacia senegal</Emphasis>

Acacia senegal is endemic to dry forest and woodland ecosystems of Sub-Saharan Africa and provides both ecological and socio-economic benefits. However, these ecosystems are threatened by escalating human disturbances and fragmentation. To investigate the human impacts on genetic diversity and structure of A. senegal, we studied genetic variability and differentiation of 330 individual trees from 11 natural A. senegal populations, grouped into lightly and heavily disturbed, using 12 polymorphic nuclear microsatellite markers. Gene diversity (H _E ) ranged from H _E = 0.570 to H _E = 0.632. Significant differences (P < 0.05) between the levels of disturbances are reported for mean gene diversity, number of alleles and allelic richness with lightly disturbed populations showing higher values. Overall, the indirect estimates of average outcrossing rates ranged from 0.794 (Kiserian) to 0.999 (Kampi ya Moto) with a mean of 0.997 suggesting a predominantly outcrossing species. There was no significant relationship (P > 0.05) detected between genetic and geographic distances, showing lack of isolation by distance. Analysis of population structure using unweighted pair group method with arithmetic mean and Bayesian model suggests presence of three gene pools as most probable, although most individuals showed mixed ancestry. The diversity and genetic structure reported in this study revealed negative impacts of human disturbance on A. senegal within this ecosystem. We recommend in-situ conservation strategies to safeguard the woodland ecosystem from further deforestation.