Landscape genetics of Acropora cf. tenuis and symbionts in the central Philippines
We densely sample corals of the key reef-building taxon Acropora cf. tenuis and their algal symbionts across a reefscape in the central Philippines in order to examine genetic variation across space and make inferences about connectivity and dispersal. We also examine neutral clustering to check for cryptic speciation (common in corals traditionally classified as Acropora tenuis).We find four genetically distinct coral taxa within our sample. All four coral taxa show genetic evidence of long distance dispersal, including weak or absent isolation by distance signals and parent-offspring pairs at widely spaced sites. These coral taxa all host a single group of algal symbionts from the genus Cladocopium, which show landscape genetic structure independent from their coral hosts. In fact, Cladocopium genetics vary with both latitude and depth, potentially indicating genome-wide local adaptation at a finer spatial scale than that seen in their hosts. Genetic variation at markedly different spatial scales between host and symbiont may be adaptive for hosts if these differences enable them to acquire symbionts adapted to their settlement environments.