Timothée Darbois has brilliantly defended his M.Sc. thesis in genetics on 2nd June. Title: A new post-glacial recolonisation route through the southwestern Alps for Pinus cembra.
His defence occurred at Ecole Normale Supérieure at Lyon.
His opponent was Dr. Christian Rellstab, Swiss Federal Research Institute WSL.
Timothée was co-supervised by Thibaut Capblancq (University Grenoble Alpes), Sébastien Laverge (CNRS) and myself. We wish him a good journey and a great race in the Alps.
Thesis abstract. Quaternary climatic oscillations greatly influenced the demographic history of species. The retrieval of tree species in glacial refugia during the Last Glacial Maximum (LGM) severely controlled their modern distribution and genetic structure. Pinus cembra, a treeline species, is thought to have recolonized the Alps after the LGM from lowland refugia in northeastern Italy. However, recent discoveries of paleo-remains and of scattered populations far above the treeline challenge this scenario. With a whole exome capture approach, we reinvestigated the species demographic history. We first excluded the possibility of in situ refugia for two atypically high-elevation populations that didn’t show any genetic compared to low-altitude populations. Results show that genetic diversity in P. cembra is mainly structured by geographic isolation, and supports the previously proposed westward recolonisation route through the Alps, from a refugium in northeastern Italy. We found that populations from the southwestern Alps were singularly differentiated from northwestern populations. Our results suggest that these southwestern populations most likely result from admixture with populations that recolonised the Alps following a different route, probably through the western Pô plain (Italy). We here showed how subtle signals of demographic history can be unravelled with genome-wide polymorphism data.