Coupling genomics with experiments to study divergence-with-gene-flow in trees

Rapid recent progress in ecological & evolutionary genomics is imparting fresh perspectives to the study of speciation, i.e. the origin and maintenance of biological diversity. A particularly active field of research at the current time is the study of ‘divergence with gene flow’, that is, divergence that involves episodes of sym- or parapatry and thus genetic contact during some stage of the process, before reproductive isolation is complete. This Ph.D. project will address key questions related to the ecological & evolutionary genomics of ‘divergence-with-gene-flow’ in Populus alba and P. tremula, two wide-spread Eurasian tree species related to Populus trichocarpa, the first completely sequenced forest tree. Defined key questions and hypotheses related to the following three topics will be addressed: (1) the roles of early vs. late-acting reproductive barriers in the maintenance of species boundaries, (2) the genomic architecture and selective value of species differences maintained in the face of gene flow, (3) the role of meiotic drive and other early post-mating barriers in species isolation. The selected topics will be addressed with the help of high-throughput ‘genotyping-by-sequencing’ approaches in natural and experimental populations. The results will be interpreted in the light of the speciation genomics literature and available data on the population genomics and evolutionary ecology of these divergent, hybridizing forest trees. By coupling genomics with experiments, I will aim to significantly advance our current understanding of these important topics in native tree species representing keystone or foundation species in terrestrial habitats.