Nature vs nurture? Light availability drives phenotypic plasticity within a reef coral species

Scleractinian corals exhibit wide intra-specific phenotypic variations. However, the extent to which these variations are explained by genotypic variation or phenotypic plasticity remains unclear. To elucidate this question, we devised a replicated experiment in which nine Montipora capitata coral colonies were cut into six pieces each, three of which were placed in shaded conditions (with a 73% reduction in light intensity) whereas the other three were kept in natural conditions as a control. After one year, we detected statistically significant morphological differences between corals of the same genotypes grown in different light environments, but no significant change in symbiont community structure. Colonies kept in control conditions exhibited high surface complexity and converged towards more digitate or corymbose morphs compared to shaded corals, which exhibited planar-like surfaces and converged toward laminar and foliose forms. Our data demonstrate the high level of light-driven phenotypic plasticity of Montipora capitata and suggest a trade-off between the amount of biomass per space area and the amount of absorption of incident light.