"Species-specific evolutionary trajectories of Pacific corals"

Abstract :

We quantified the standing genetic diversity of three coral morphospecies - Porites lobata, Pocillopora meandrina, and Millepora platyphylla - in relation to past sea temperature variations across their Pacific spread, as part of the Tara Pacific Expedition. Coral specimens with the targeted colony morphologies were sampled across 11 islands on an 18,000 km longitudinal transect of the Pacific Ocean, and either genome-wide (Porites, Pocillopora) or targeted (Millepora) SNPs were obtained for 109, 103, and 57 colonies, respectively.

Within the targeted morphologies, 3 and 5 independent genetic lineages/species were identified in Porites and Pocillopora respectively, highlighting the difficulty of morphology-based sampling in corals. Contrastingly, all Millepora samples belonged to the targeted species.

The biogeographical distribution of these lineages was distinct for each genus. These different biogeographical patterns in the same oceanographical context do question the relation of these genera to the environment. We showed that significantly less past temperature outlier SNPs were included in genomic islands of differentiation and under divergent selection among species in Porites than in Pocillopora.

This lesser genomic signature to prevailing environments in Porites argues for a built-in stress tolerance, whereas the stronger genomic imprint by the environment on Pocillopora may point to a stronger adaptation to different niches, making it more sensitive to climate perturbations. Within the context of conservation, Millepora, with its high within species biogeographic structuring, will require more reefs to be preserved to protect its extant diversity. These recently published results ( https://www.nature.com/articles/s44185-023-00020-8 ) show that reef conservation will require species-specific strategies.

Authors: CR Voolstra*, BCC Hume*, EJ Armstrong*, G Mitushasi, B Porro, N Oury, S Agostini, E Boissin, J Poulain, Q Carradec, DA Paz-García, D Zoccola, H Magalon, C Moulin, G Bourdin, G Iwankow, S Romac, Tara Pacific Consortium Coordinators, S Planes, D Allemand, D Forcioli*. (*equal contribution)