Same places, same stories? Genomics reveals similar structuring and demographic patterns for four Pocillopora coral species in the southwestern Indian Ocean

Aim: Efficiently protecting species requires knowing their ecological, life-history and reproductive traits. This is particularly decisive for scleractinian corals, key components of coral reefs, which are experiencing critical declines. Yet their connectivity remains insufficiently documented. Here, we focused on four distinct species of the coral genus Pocillopora found in diverse habitats of the southwestern Indian Ocean and presenting various reproductive strategies. We aimed to understand whether these traits affect species connectivity.Location: Archipelagos and islands of the southwestern Indian Ocean.Taxon: Pocillopora spp.Methods: We used target capture to collect single-nucleotide polymorphisms (SNPs) from over a thousand colonies sampled across nine localities. From the ca. 1400 SNPs retained per species, Bayesian clustering methods, networks and demographic inferences were applied to first infer the population genetic structure and connectivity of each species, then the demographic history of each population.Results: All four Pocillopora species exhibited almost the same genetic structuring pattern, reflecting the sampled ecoregions (Madagascar and surrounding islands vs. Mascarene Islands). However, the genetic differentiation was stronger (F-ST about 10 times higher) for P. acuta, the species inhabiting more enclosed habitats, such as lagoons and shallow waters, and reproducing mainly asexually. Similarly, all populations, except those from P. acuta, showed a signature of population expansion ca. 100,000 years ago, following the penultimate glacial period.Main Conclusions: These results indicate reduced gene flow between Madagascar and the Mascarene Islands, probably linked to currents, suggesting distinct connectivity networks that should be considered independently when setting up conservation plans. In addition, shared demographic histories reflect that populations from these species have probably met the same environmental constraints and reacted similarly, something that should be considered in light of the ongoing rapid climate change.