Relationships between population density, fine-scale genetic structure, mating system and pollen dispersal in a timber tree from African rainforest

Also published at Bioversity International

Authors: Duminil, J.; Dainou, K.; Kaviriri, D.K.; Gillet, P.; Loo, J.; Doucet, J.L.; Hardy, O.J.

The reproductive biology and genetic diversity of trees in the Congo Basin don’t seem to be affected by current logging practices. However, researcher recommend further investigations in low-density populations to evaluate (1) whether pollen limitation may reduce seed production and (2) the regeneration potential of the species.

This is the result from a study of genetic diversity, mating system and gene flow in three Central African populations of the self-compatible legume timber species Erythrophleum suaveolens with contrasting densities (0.11, 0.68 and 1.72 adults per ha).

Comparing reproductive biology processes and genetic diversity of populations at different densities can provide indirect evidence of the potential impacts of logging.

Selective logging could affect the demography, reproductive biology and evolutionary potential of forest trees. This is particularly relevant in tropical forests where natural population densities can be low and isolated trees may be subject to outcross pollen limitation and/or produce low-quality selfed seeds that exhibit inbreeding depression.

Researchers found that inbred individuals are eliminated between seedling and adult stages. Levels of genetic diversity, selfing rates (~16%) and patterns of spatial genetic structure (Sp ~0.006) were similar in all three populations.

However, the extent of gene dispersal differed markedly among populations: the average distance of pollen dispersal increased with decreasing density (from 200 m in the high-density population to 1000 m in the low-density one). In other words, at lower population densities, trees are still connected as a result of larger pollen dispersal distances.

The study was conducted by Bioversity International, the Université Libre de Bruxelles, Brussels, Belgium; Université de Liège, Gembloux, Belgium; Nature+ asbl, Wavre, Belgium; Université de Kisangani, Kisangani, Democratic Republic of Congo.