Format: ORAL

Juan M. Gorospe1,2, Elika Zvesk2, Desalegn Chala3, Abel Gizaw3, Lubomr Pilek4, Filip Kolr1,2,3, Christian Brochmann3, Roswitha Schmickl1,2

1, Charles University, Prague, Czech Republic 2, Institute of Botany of The Czech Academy of Sciences, Pruhonice, Czech Republic 3, University of Oslo, Oslo, Norway 4, University of South Bohemia, Ceske Budejovice, Czech Republic

Mountains are dynamic regions that undergo tectonic, erosional and climatic processes over a short geological time period. These processes make mountainous regions highly heterogeneous environments with a wide variety of topographic features. Such habitat heterogeneity and dynamics generate increased opportunities for lineage differentiation through ecological adaptation, geographic isolation and secondary contact. The afroalpine vegetation belts on the top of the East African mountains are highly isolated both geographically and ecologically, which makes them a great system to study evolution and speciation. The genus Dendrosenecio evolved independently in four geographically isolated afroalpine mountain groups, mainly as a consequence of reduced gene flow between these mountain groups. At the same time, populations of different Dendrosenecio species are sometimes found in sympatry, which could be evidence for ecological speciation. In this study, we focus on two sister species, D. keniensis and D. keniodendron, that likely evolved on Mount Kenya and show clear differences in morphology, flower phenology, reproduction and ecology. These species can be found growing sympatrically, and the existence of a hybrid zone has been reported. We employed vegetation plot information and dd-RADseq data together with population genomic tools to evaluate the extent of habitat differences, genetic differentiation, and the demographic processes involved in the divergence between these two species. In particular, habitat similarity between the two species on Mount Kenya were analysed, genetic differentiation between them was evaluated, and ecological speciation was tested against geographic speciation followed by secondary contact. Vegetation plot data showed a negative relationship between both species, genetic differentiation supported two well differentiated groups, and demographic modelling supported a speciation-with-gene flow scenario. Taken together, these results suggest that ecologically mediated speciation occurred between these two Dendrosenecio species from Mt. Kenya.