Molecular trade-offs between adaptation to salinity and immunity in three-spined sticklebacks
Climate change and its consequences on the oceans represent major challenges for marine species, which either need to migrate to remain in their optimal niche or need to adapt to avoid extinction. While the genetics and genomics of adaptation are well studied to predict the future state of marine biodiversity, major gaps remain about the role and mechanisms of phenotypic plasticity within and across generations. Particularly, climate change is multifold and non-parallel stressors limit evolution: indeed, organisms cannot allocate infinite resources into all responses, and trade-offs therefore emerge. Because stressors are often investigated in isolation, our overall understanding of molecular trade-offs is limited. In this project, we will study the impact of two major concomitant challenges induced by climate change, namely the change in ocean salinity and the associated change in the parasite community. We will use the three-spined stickleback (Gasterosteus aculeatus) fish from the Baltic Sea, which has been coined a “time machine” because of its rapid salinity change mimicking the future of the oceans. We will investigate the osmoregulation-immunity trade-offs mediated by DNA methylation. After identifying these trade-offs, we will use a network approach to shed lights on the interactions of methylation within gene clusters, and their expression (RNA-seq). We will use data generated by the hosting group on (1) natural populations of the Baltic Sea and (2) experimental acclimation to salinity, completed by a common garden experiment testing the induction of trade-offs by both parasite infection and salinity change. This project will advance our understanding of the mechanisms of phenotypic plasticity in marine organisms and their consequences on adaptive evolution.