Population structure and clonal prevalence of scleractinian corals (Montipora capitata and Porites compressa) in Kaneohe Bay, Oahu

As the effects of anthropogenic climate change grow, mass coral bleaching events are expected to increase in severity and extent. Much research has focused on the environmental stressors themselves, symbiotic community compositions, and transcriptomics of the coral host. Globally, fine-scale population structure of corals is understudied. This study reports patterns of population structure and clonal prevalence found in Montipora capitata and Porites compressa in Kaneohe Bay, Oahu. Generated using ddRAD methods, genetic data reveals different patterns in each taxa despite them being exposed to the same environmental conditions. STRUCTURE and site-level pairwise FST analyses suggest population structure in M. capitata resembling isolation by distance. Mantel tests show strong, significant FST correlations in M. capitata in relation to geographic distance, water residence time, and salinity and temperature variability (range) at different time scales. STRUCTURE did not reveal strong population structure in P. compressa. FST correlation was found in P. compressa in relation to yearly average sea surface height. We also report high prevalence of clonal colonies in P. compressa in outer bay sites exposed to storms and high energy swells. Amongst only outer bay sites, 7 out of 23 sequenced individuals were clones of other colonies. Amongst all 47 sequenced P. compressa individuals, 8 were clones. Only one clone was detected in M. capitata. Moving forward, it is crucial to consider these preexisting patterns relating to genetic diversity when planning and executing conservation and restoration initiatives. Recognizing that there are differences in population structure and diversity between coral taxa, even on such small-scales, is important as it suggests that small-scale reefs must be managed by species rather than by geography.