Population genomics of the Mediterranean red gorgonian, Paramuricea clavata

Intraspecific genetic diversity is a fundamental level of biodiversity. The need to focus conservation efforts on genetic diversity has been recently strengthened, owing to the potential link between genetic diversity and adaptive capacities to climate change. The Mediterranean red gorgonian, Paramuricea clavata is characterized by low population dynamics (few mm per year), late sexual maturity (10-12 years of age) and restricted dispersal abilities (10s of m). This species harbors a key ecological role as habitat-forming species in biodiversity rich coralligenous communities. In the last 20 years, P. clavata has been recurrently impacted by dramatic mass mortality events linked to marine heat waves. These events induced tissue necrosis potentially driving individuals to death. In this context, the evolutionary trajectory of P. clavata is questioned with potential negative impacts on associated coralligenous communities. Interestingly, field surveys conducted during the MMEs suggest that individuals of P. clavata were differentially affected by tissue necrosis with individuals potentially less sensitive to thermal anomalies. This result opens the possibility to develop warming-resilient restoration actions. Previous studies based on microsatellites provided important insights regarding for instance the restricted connectivity of the species or the potential link between genetic drift and sensitivity of populations to thermal stress. Yet, various issues remain to be solved to develop restoration actions. For instance, little is known regarding the strength of adaptive divergence among populations. The occurrence of genetic factors driving the differential response among individuals observed during mortality events remain to be tested. Here, I will address some of these issues by presenting the results of a study combining a trans-regional thermal stress experiment involving 12 populations from 5 regions of the Mediterranean and whole-genome resequencing targeting a subset of 120 individuals. I will discuss the potential implications of these results for the conservation of the species.