Martin Lascoux has a PhD in Genetics from Paris-Saclay University (1992) and was a postdoctoral fellow at University of Wisconsin-Madison. Since 2001 he is a Professor of population genetics at Uppsala University, Sweden. His work focuses on population genetics inferences, local adaptation, molecular evolution and the evolution of polyploidy.
All organisms experienced cyclical changes in climate and environmental disturbances during their evolutionary history and this constitutes a natural testing ground of their resilience. It has become common place to state that trees, in general, and forest trees, in particular, are ill-equipped to face climate change, the main argument being that their long generation-time will prevent them from adapting fast enough to rapid climate change. But is it really so? In the present talk we will give two examples that illustrate that forest trees, and European oaks among them, appear more resilient than anticipated. In the first study, we used exome capture data to reconstruct past changes in effective population size, Ne, of seven major forest tree species. All seven species exhibited continuous increase in Ne over long periods of time. For some species, Quercus petraea and Fagus sylvatica, this time period extended very far back in time (up to 15 Mya in Quercus petraea). Both species had a very large current Ne, especially Quercus petraea (800,000). Interestingly, Ne trajectories of the seven species can be clustered into three groups, suggesting that they were not entirely determined by environmental factors. The second study considers a much shorter time scale. We used a retrospective approach to monitor genomic changes in oak trees since the Little Ice Age (LIA, around 300-400 years ago). Allelic frequency changes were assessed from whole-genome pooled sequences for four age-structured cohorts of sessile oak (Quercus petraea) dating back to 1680, in each of three different oak forests in France. We found evidence of parallel linked selection in the three forests during the late LIA, and a shift of selection during more recent time periods of the Anthropocene. Hence, the two studies suggest that trees have been able to maintain their evolutionary potential over very long periods of time and that this resilience could be due, at least in part, to their ability to respond quickly to new environmental challenges.
