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Curr Biol. 2018 Aug 20;28(16):2570-2580.e6. doi: 10.1016/j.cub.2018.07.008. Epub 2018 Aug 9.

Systematic Revision of Symbiodiniaceae Highlights the Antiquity and Diversity of Coral Endosymbionts.

Author information

1
Department of Biology, The Pennsylvania State University, 208 Mueller Laboratory, University Park, PA 16802, USA. Electronic address: tcl3@psu.edu.
2
Department of Integrative Biology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331, USA. Electronic address: parkinjo@oregonstate.edu.
3
Herbarium and Biology Department, University of North Carolina-Chapel Hill, Coker Hall, CB 3280, Chapel Hill, NC 27599, USA.
4
School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul 151-747, Republic of Korea; Advanced Institutes of Convergence Technology, Suwon, Gyeonggi-do 16229, Republic of Korea.
5
Molecular Invertebrate Systematics and Ecology Laboratory, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan.
6
Red Sea Research Center, Division of Biological and Environmental Science and Engineering (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
7
Department of Biological Sciences and Molette Laboratory for Climate Change and Environmental Studies, Auburn University, 101 Rouse Life Sciences Building, Auburn, AL 36849, USA.

Abstract

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.

KEYWORDS:

Mesozoic; Symbiodinium; clades; genera; molecular clock; systematics; taxonomy; zooxanthellae

PMID:
30100341
DOI:
10.1016/j.cub.2018.07.008
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