Vetter, J.; Reichert, J.; Dietzmann, A.; Hahn, L.; Lang, A. E.; Puntin, G.; Ziegler, M.

Coral biodiversity has an enhancing but saturating effect on community productivity, however, the direct effects of neighbouring coral colonies on productivity remain poorly understood due to the complex interplay of biotic and abiotic factors. We set up a fully controlled aquarium experiment, in which we quantified the effects of species identity and composition on the productivity of nine stony coral species from three families. Baseline productivity and the response to neighbouring organisms strongly differed between species. Regardless of whether species increased or decreased productivity, the responses were consistently more pronounced and positive towards conspecific than heterospecific neighbours, indicating kin selection effects between closely related species. Species productivity in monoculture and productivity in polyculture were inversely correlated, with inherently less productive species overperforming in polyculture and vice versa. Our results highlight that contact-free interactions in marine animals shape biodiversity-productivity effects otherwise known from plant communities.