Non-timber Forest Product Harvest does not Affect the Genetic Diversity of a Tropical Tree Despite Negative Effects on Population Fitness

The level of genetic diversity in a population can affect ecological processes and plant responses to disturbance. In turn, disturbance can alter population genetic diversity and structure. Populations in fragmented and logged habitats often show reduced genetic diversity and increased inbreeding and differentiation. Long-term harvesting of wild plants (for foliage, bark, and roots), can affect population genetic diversity by altering individual fitness and genetic contribution. Our understanding of these changes in genetic diversity due to the harvesting of plant organs is still limited. We used nine microsatellite markers to study the effect of long-term bark and foliage harvest by Fulani people on the genetic diversity and structure of 12 populations of African mahogany (Khaya senegalensis) in Benin. We sampled 20 individuals in each population to test the effect of harvesting. For each population, we divided the samples equally between seedling and adults to test if the effects are stronger in seedlings. We found moderate genetic diversity (He = 0.53 0.04) and weak but significant differentiation among local populations (FST = 0.043, P < 0.001). There was no significant effect of harvest on genetic diversity or structure, although previous work found significant negative effects of harvest on the reproduction of adults, offspring density, and population fitness. Our results suggest that demographic responses to disturbance precede a detectable genetic response. Future studies should focus on using parentage analysis to test if genotypes of harvested parents are directly represented in the offspring populations.