title: Microbial invasion of the Caribbean by an Indo-Pacific coral zooxanthella.
abstract: Human-induced environmental changes have ushered in the rapid decline of coral reef ecosystems, particularly by disrupting the symbioses between reef-building corals and their photosymbionts. However, escalating stressful conditions enable some symbionts to thrive as opportunists. We present evidence that a stress-tolerant "zooxanthella" from the Indo-Pacific Ocean, Symbiodinium trenchii, has rapidly spread to coral communities across the Greater Caribbean. In marked contrast to populations from the Indo-Pacific, Atlantic populations of S. trenchii contained exceptionally low genetic diversity, including several widespread and genetically similar clones. Colonies with this symbiont tolerate temperatures 1-2 °C higher than other host-symbiont combinations; however, calcification by hosts harboring S. trenchii is reduced by nearly half, compared with those harboring natives, and suggests that these new symbioses are maladapted. Unforeseen opportunism and geographical expansion by invasive mutualistic microbes could profoundly influence the response of reef coral symbioses to major environmental perturbations but may ultimately compromise ecosystem stability and function.
authors.affiliation: Department of Biology, The Pennsylvania State University, University Park, PA 16802; College of Earth, Ocean, and Environment, University of Delaware, Lewes, DE 19958; tcl3@psu.edu tpettay@udel.edu.
authors.forename: D Tye
authors.initials: DT
authors.lastname: Pettay
authors.affiliation: Department of Biology, The Pennsylvania State University, University Park, PA 16802;
authors.forename: Drew C
authors.initials: DC
authors.lastname: Wham
authors.affiliation: Unidad Académica de Sistemas Arrecifales (Puerto Morelos), Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, CP 77500 Cancún, Mexico; Science Under Sail Institute for Exploration, Sarasota, FL 34230;
authors.forename: Robin T
authors.initials: RT
authors.lastname: Smith
authors.affiliation: Unidad Académica de Sistemas Arrecifales (Puerto Morelos), Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, CP 77500 Cancún, Mexico;
authors.forename: Roberto
authors.initials: R
authors.lastname: Iglesias-Prieto
authors.affiliation: Department of Biology, The Pennsylvania State University, University Park, PA 16802; Penn State Institutes of Energy and the Environment, University Park, PA 16802 tcl3@psu.edu tpettay@udel.edu.
authors.forename: Todd C
authors.identifier: 0000-0001-7607-9358
authors.initials: TC
authors.lastname: LaJeunesse
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000469:parasitology*; D017691:Caribbean Region; D057231:Climate Change; D057894:Coral Reefs; D004141:Dinoflagellida / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D017753:Ecosystem; D014644:Genetic Variation; D006801:Humans; D019156:Indian Ocean; D058865:Introduced Species; D010140:Pacific Ocean; D013559:Symbiosis
keywords: calcification; climate change; invasive species; reef corals; symbiosis