Speciation theory assumes that evolutionary change accumulates over space and time, either as a result of mutation-order or ecological speciation. While both mechanisms are theoretically plausible, the predominant speciation mode remains unknown for most species. Isolated mountain massifs are especially appealing to study speciation as both adaptive and non-adaptive processes are expected to co-occur. While diversification in montane systems has mainly been treated as a forward-directed, vertical process, genomic evidence suggests that speciation can also be strongly
affected by introgression, horizontal (lateral) gene transfer, or genetic rescue. Using East African white-eyes (genus Zosterops) as an avian model, we here address to what extent (i) highlandlowland speciation is driven by mutation-order and/or ecological speciation; and (ii) sudden environmental changes may have affected horizontal (lateral) processes in the diversification of this taxon. We hereby capitalize on state-of-the-art developments in genomics and simulation modeling. The project will be conducted in a study area (4 Kenyan sky islands) which is very well documented for its local and rapid ecological changes over the past million years, and on a bird genus (Zosterops) known as a classic “great speciator” lineage. The project is expected to yield highly-innovative insights into putative effects of horizontal processes on past speciation, and ultimately, into the genomic basis of avian speciation.