Award: OCE-1737312

The goal of the project was to determine which natural environmental factors affect corals the most, to the extent that surviving these environmental pressures requires genetic adaptation. The idea was to align genetic differences among corals sampled from different reef sites with environmental differences between these sites, and thus identify the key environmental drivers of genetic divergence. The project brought many unexpected results. First and foremost, we found that each of the four coral species that we studied were in fact composed of 3 or 4 genetically distinct lineages. These lineages appear to exchange genetic material but maintain their identity since a substantial fraction of the genome is protected from such exchange. This situation is novel in coral biology, and the underlying mechanisms are unknown. Within each species, the cryptic lineages are also ecologically distinct. Each nominal species contains one or two lineages specialized for deeper reef habitat (>10m). Ecological distinction between the two shallow lineages is harder to interpret and will require follow-up confirmatory studies, but it appears to align with the influence of the Florida Bay on the reef system. Overall, the project did reveal the key environmental gradients driving coral adaptation: depth and Florida Bay influence. The unexpected genetic structure within each species and mechanisms that generated and maintain it are exciting subjects for future research. Other outcomes include development of two novel methodologies to analyze genetic data, ?LD networks? and ?Multimodel demographic inference?, which have been made available for unrestricted use as GitHub repositories. We have also published all the underwater footage from the 63 Florida Keys reefs that we visited as an interactive Maptour website. Broader impacts include relevance for reef management and restoration: the key factors affecting coral fitness that we have identified can be now taken into account when identifying suitable restoration sites and sourcing colonies to restore them. Our results also show that we have three fold more ecologically distinct coral lineages to manage and protect compared to the number of nominal species. The project is the main theme for two female graduate students (one of them Pacific Islander), and provided extensive lab and bioinformatics training opportunities for several undergraduates. Last Modified: 12/31/2021 Submitted by: Mikhail V Matz