Shaping coral traits: plasticity more than filtering

The structure of an ecosystem is usually determined by the shape of the organisms that build it, commonly known as ecosystem engineers. Understanding to what extent plasticity and environmental filtering determine variation in the physical structure of ecosystem engineers is necessary to predict how ecosystem structure may change. Here, we explored coral survival and the plasticity of morphological traits that are critical for habitat provision in coral reefs. We conducted a reciprocal clonal transplant experiment in which branching corals from the genera Porites and Acropora were moved to and from a deep and a shallow site within a lagoon in the Maldives. Survival and trait analyses revealed that transplant destination consistently induced the strongest changes, particularly among Acropora spp. The origin of the corals had only marginal effects on some of the traits. We also detected variation in the way individuals from the same species and site differentiate in their shape, showing that traits linked to habitat provision are phenotypically plastic. The results suggest that in the quite common lagoonal conditions studied here, coral phenotypic plasticity plays a stronger role than environmental filtering, in determining the zonation of coral morphologies, and consequently the habitats they provide for other organisms.