Adaptive processes in cnidarians : integrative study of the response to thermal stress and climate change, from genes to populations – ADACNI

The study of adaptative response to disturbances is central in evolutionary biology, especially in the current context of climate change. Cnidarians are ecologically important species which face this adaptive challenge. Our project aims at studying (i) the adaptability and adaptation mechanisms to thermal stress in sessile cnidarians, and (ii) the ecological and evolutionary consequences of variability in adaptation abilities. The adaptation will be envisioned through its different levels of acceptation: individual acclimatization, variation in acclimatization via epigenetic processes, genetic adaptation through selection at the population level, or an interaction between these processes. A comparative framework will be used from the individual to the species level. We will thus test if species from more variable environments present a more efficient response to thermal stress than those from stable conditions. The compared species will be the sea anemone Anemonia viridis (eurytherm, symbiotic), the tropical coral Pocillopora damicornis (stenotherm, symbiotic) and the Mediterranean red coral Corallium rubrum (eurytherm, non symbiotic). Thermal stress has been linked to bleaching in P. damicornis and A. viridis, and to necrosis and mortality events in C. rubrum. For each species we will compare populations from different temperature regimes and we will test the importance of plasticity and genetic determinism in the adaptation to spatial and temporal environmental heterogeneity. First an experimental approach will be used to study the transcriptomic response in stress situation for the different comparisons envisioned. In addition, the application of recurrent stress will allow us to study the involvement epigenetic processes, from the phenotypic response to the underlying molecular mechanisms. A population genetic approach based on high-throughput SNP genotyping will be used to search outlier loci which could be responsible for genetic adaptation of one species to different environments. The third part of the project will be used to verify if the genes identified in the transcriptomic and the population analyzes are indeed involved in the response to stress. This validation will be done experimentally with a sufficient number of individuals and by the study of individuals with necrosis or bleaching symptoms in natural conditions. A modeling approach will be used to envision the response of populations and species to climate change, including the evolution of plasticity itself. The obtained results will be useful for the management of natural populations. They will also give important information for the study of the evolution of adaptive processes in metazoans.