Abstract
Coral biodiversity can enhance community productivity; however, the direct effects of inter- and intraspecific neighbouring coral colonies on productivity remain poorly understood due to the complex interplay of biotic and abiotic factors. Here, we set up a fully controlled incubation experiment, where we quantified the effects of species identity and composition on the photosynthesis, respiration, and calcification as proxies for productivity of nine stony coral species from three families. Baseline productivity varied strongly between species. Several corals responded to neighbouring colonies without direct contact, suggesting that they may detect nearby individuals and potentially adjust their physiological activity. Regardless of whether species increased or decreased productivity, the responses were consistently more pronounced and positive towards conspecific than heterospecific neighbours, indicating potential kin selection effects between members of the same species. Notably, species with lower productivity in monoculture tended to exceed expectations in polyculture, while species that were highly productive in monoculture often underperformed in multispecies assemblages. Our results highlight that contact-free interactions in marine animals may shape biodiversity-productivity effects otherwise known from plant communities. Therefore, neighbour-specific interactions should be considered when designing coral reef restoration approaches, as they may influence the success of different species and assemblages.