Estimates of gene flow in forest trees

Abstract

Qualitative and quantitative estimates of gene flow were obtained for fourteen gymnosperm and seven angiosperm forest tree species. High levels of gene flow were prevalent among gymnosperms while these levels varied from high to low among angiosperms. In both groups, species with greater pollen dispersal abilities appear to maintain high levels of gene flow. A detailed analysis of population structure in relation to gene flow was carried out on a gymnosperm species (Pinus rigida) and two angiosperm subspecies (Eucalyptus caesia ssp. caesia and ssp. magna). The results suggested that populations of many species may be concatenated systems bound by gene flow, and the overall levels of gene flow may be influenced by either single or clusters of populations. Different levels of gene flow was found between two closely related species of E. caesia growing under similar ecological conditions, suggesting a plausible link between pollinator behaviour and pollen flow.