Data from: Systematic revision of Symbiodiniaceae highlights the antiquity and diversity of coral endosymbionts

The advent of molecular data has transformed the science of organizing and studying life on Earth. Genetics-based evidence provides fundamental insights into the diversity, ecology, and origins of many biological systems, including the mutualisms between metazoan hosts and their micro-algal partners. A well-known example is the dinoflagellate endosymbionts (“zooxanthellae”) that power the growth of stony corals and coral reef ecosystems. Once assumed to encompass a single panmictic species, genetic evidence has revealed a divergent and rich diversity within the zooxanthella genus Symbiodinium. Despite decades of reporting on the significance of this diversity, the formal systematics of these eukaryotic microbes have not kept pace, and a major revision is long overdue. With the consideration of molecular, morphological, physiological, and ecological data, we propose that evolutionarily divergent Symbiodinium “clades” are equivalent to genera in the family Symbiodiniaceae, of which we provide formal descriptions for seven. Additionally, we recalibrate the molecular clock for the group and amend the date for the earliest diversification of this family to the middle of the Mesozoic Era (~ 160 Ma). This timing corresponds with the adaptive radiation of analogs to modern shallow–water stony corals during the Jurassic Period and connects the rise of symbiotic dinoflagellates with the emergence and evolutionary success of reef-building corals. This improved taxonomic framework acknowledges the symbiont group’s long evolutionary history while filling a pronounced taxonomic gap. Its adoption will improve scientific dialog and future research on the physiology, ecology, and evolution of these important micro-algae.