title: Ancestral genetic diversity associated with the rapid spread of stress-tolerant coral symbionts in response to Holocene climate change.
abstract: Coral communities in the Persian/Arabian Gulf (PAG) withstand unusually high salinity levels and regular summer temperature maxima of up to ∼35 °C that kill conspecifics elsewhere. Due to the recent formation of the PAG and its subsequent shift to a hot climate, these corals have had only <6,000 y to adapt to these extreme conditions and can therefore inform on how coral reefs may respond to global warming. One key to coral survival in the world's warmest reefs are symbioses with a newly discovered alga,Symbiodinium thermophilum Currently, it is unknown whether this symbiont originated elsewhere or emerged from unexpectedly fast evolution catalyzed by the extreme environment. Analyzing genetic diversity of symbiotic algae across >5,000 km of the PAG, the Gulf of Oman, and the Red Sea coastline, we show thatS. thermophilumis a member of a highly diverse, ancient group of symbionts cryptically distributed outside the PAG. We argue that the adjustment to temperature extremes by PAG corals was facilitated by the positive selection of preadapted symbionts. Our findings suggest that maintaining the largest possible pool of potentially stress-tolerant genotypes by protecting existing biodiversity is crucial to promote rapid adaptation to present-day climate change, not only for coral reefs, but for ecosystems in general.
authors.affiliation: Coral Reef Laboratory, Ocean and Earth Science, University of Southampton, Southampton SO14 3ZH, United Kingdom;
authors.forename: Benjamin C C
authors.initials: BC
authors.lastname: Hume
authors.affiliation: Red Sea Research Center, Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia;
authors.forename: Christian R
authors.initials: CR
authors.lastname: Voolstra
authors.affiliation: Red Sea Research Center, Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia;
authors.forename: Chatchanit
authors.initials: C
authors.lastname: Arif
authors.affiliation: Coral Reef Laboratory, Ocean and Earth Science, University of Southampton, Southampton SO14 3ZH, United Kingdom; Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom;
authors.forename: Cecilia
authors.initials: C
authors.lastname: D'Angelo
authors.affiliation: Marine Biology Laboratory, Centre for Genomics and Systems Biology, New York University Abu Dhabi, Abu Dhabi 129188, United Arab Emirates;
authors.forename: John A
authors.initials: JA
authors.lastname: Burt
authors.affiliation: Department of Zoology, Tel Aviv University, Tel Aviv 6997801, Israel; The Interuniversity Institute for Marine Sciences in Eilat, Eilat 8810369, Israel.
authors.forename: Gal
authors.initials: G
authors.lastname: Eyal
authors.affiliation: Department of Zoology, Tel Aviv University, Tel Aviv 6997801, Israel;
authors.forename: Yossi
authors.initials: Y
authors.lastname: Loya
authors.affiliation: Coral Reef Laboratory, Ocean and Earth Science, University of Southampton, Southampton SO14 3ZH, United Kingdom; Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, United Kingdom; joerg.wiedenmann@noc.soton.ac.uk.
authors.forename: Jörg
authors.initials: J
authors.lastname: Wiedenmann
mesh_terms: D000818:Animals; D037421:Anthozoa; D004141:Dinoflagellida / Q000235:genetics*; D017753:Ecosystem; D014644:Genetic Variation; D009792:Oceans and Seas; D054712:Salinity; D013312:Stress, Physiological; D013559:Symbiosis
keywords: Persian/Arabian Gulf; Symbiodinium; adaptation; climate change; coral