Characterizing the adaptive potential of north-western Pacific reef corals to empower conservation strategies: a role for seascape genomics

Abstract

Coral reefs are suffering a major decline due to the environmental constraints imposed by climate change. Over the last 20 years, three major coral bleaching events occurred in concomitance of anomalous heat waves, provoking a severe loss of coral cover world-wide. Recent works, however, reported of reefs at which recurrent bleaching events resulted in reduced sensitivity to thermal stresses. Adaptation has been suggested to be responsible for this phenomenon. The conservation strategies for preserving the reefs, as they are conceived now, can not cope with global climatic shifts. In this regard, researchers advocated the set-up of a preservation framework to reinforce coral adaptive potential. The main obstacle to this approach is that studies focusing on coral adaptation usually concern a couple of contrasted reefs and their results are therefore hard to generalize at the scale of a reef system. In this work, we ran a seascape genomics analysis to study adaptation of a flagship coral species of the Ryukyu Archipelago (Japan). By associating genotype frequencies with descriptors of historical environmental conditions, we discovered six polymorphisms that might elicit resistance against thermal stress and calculated the probability of presence of these putative adaptive traits across the whole study area. Furthermore, the seascape genomics method allowed us to calculate a connectivity model based on sea surface currents and calibrated on genetic data. These results were used to compute, for every reef of the Ryukyu Archipelago, indexes describing corals adaptive and connective potential. This information can be extremely useful for preservation, since it provides an objective information on how the adaptive potential distributes and disperse across the reef system. Finally, we provide two examples of how this information can be implemented in conservation strategies commonly used such as the establishment of marine protected areas and coral nurseries. Together, the results of our work advocate the value of genetic analyses for empowering preservation efforts dedicated to the protection of coral reef from warming oceans.