Department of Biology, The Pennsylvania State University, 208 Mueller Laboratory, University Park, PA 16802, USA.
Department of Integrative Biology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331, USA.
Curr Biol. 2018 Aug 20;28(16):2570-2580.e6. doi: 10.1016/j.cub.2018.07.008. Epub 2018 Aug 9.
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, and we provide formal descriptions for seven of them. 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 mya). This timing corresponds with the adaptive radiation of analogs to modern shallow-water stony corals during the Jurassic Period and connects the rise of these symbiotic dinoflagellates with the emergence and evolutionary success of reef-building corals. This improved framework acknowledges the Symbiodiniaceae's long evolutionary history while filling a pronounced taxonomic gap. Its adoption will facilitate scientific dialog and future research on the physiology, ecology, and evolution of these important micro-algae.
分子数据的出现改变了组织和研究地球上生命的科学。基于遗传学的证据为许多生物系统的多样性、生态学和起源提供了基本的见解，包括后生动物宿主与其微藻伙伴之间的共生关系。一个著名的例子是甲藻内共生体（“虫黄藻”），它为石珊瑚和珊瑚礁生态系统的生长提供动力。曾经被认为只包含一个单一的混合物种，但遗传证据揭示了虫黄藻属 Symbiodinium 内的分歧和丰富的多样性。尽管几十年来一直在报道这种多样性的重要性，但这些真核微生物的正式分类学并没有跟上步伐，因此早就应该进行重大修订。考虑到分子、形态、生理和生态数据，我们提出进化上不同的 Symbiodinium“分支”相当于 Symbiodiniaceae 科中的属，并且我们为其中的七个属提供了正式描述。此外，我们重新校准了该组的分子钟，并将该家族最早多样化的日期修正为中生代中期（约 1.60 亿年前）。这一时间与侏罗纪时期现代浅海石珊瑚的类似物的适应性辐射相吻合，并将这些共生甲藻的兴起与造礁珊瑚的出现和进化成功联系起来。这个改进的框架承认了 Symbiodiniaceae 的悠久进化历史，同时填补了明显的分类学空白。它的采用将有助于关于这些重要微藻的生理学、生态学和进化的科学对话和未来研究。
