Pettay D Tye, Lajeunesse Todd C
Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America ; College of Earth, Ocean, and Environment, University of Delaware, Lewes, Delaware, United States of America.
PLoS One. 2013 Nov 5;8(11):e79208. doi: 10.1371/journal.pone.0079208. eCollection 2013.
The migration and dispersal of stress-tolerant symbiotic dinoflagellates (genus Symbiodinium) may influence the response of symbiotic reef-building corals to a warming climate. We analyzed the genetic structure of the stress-tolerant endosymbiont, Symbiodinium glynni nomen nudum (ITS2 - D1), obtained from Pocillopora colonies that dominate eastern Pacific coral communities. Eleven microsatellite loci identified genotypically diverse populations with minimal genetic subdivision throughout the Eastern Tropical Pacific, encompassing 1000's of square kilometers from mainland Mexico to the Galapagos Islands. The lack of population differentiation over these distances corresponds with extensive regional host connectivity and indicates that Pocillopora larvae, which maternally inherit their symbionts, aid in the dispersal of this symbiont. In contrast to its host, however, subtropical populations of S. glynni in the Gulf of California (Sea of Cortez) were strongly differentiated from populations in tropical eastern Pacific. Selection pressures related to large seasonal fluctuations in temperature and irradiance likely explain this abrupt genetic discontinuity. We infer that S. glynni genotypes harbored by host larvae arriving from more southern locations are rapidly replaced by genotypes adapted to more temperate environments. The strong population structure of S. glynni corresponds with fluctuating environmental conditions and suggests that these genetically diverse populations have the potential to evolve rapidly to changing environments and reveals the importance of environmental extremes in driving microbial eukaryote (e.g., plankton) speciation in marine ecosystems.
耐胁迫共生甲藻（共生藻属）的迁移和扩散可能会影响造礁共生珊瑚对气候变暖的响应。我们分析了从构成东太平洋珊瑚群落主体的鹿角杯形珊瑚群体中获得的耐胁迫内共生体——裸名格氏共生藻（ITS2 - D1）的遗传结构。11个微卫星位点确定了基因型多样的群体，在整个东热带太平洋地区遗传分化极小，范围涵盖从墨西哥大陆到加拉帕戈斯群岛的数千平方公里区域。在这些距离上缺乏种群分化与广泛的区域宿主连通性相一致，这表明通过母体遗传共生体的鹿角杯形珊瑚幼虫有助于这种共生体的扩散。然而，与其宿主不同的是，加利福尼亚湾（科尔特斯海）的亚热带格氏共生藻种群与热带东太平洋的种群有强烈分化。与温度和光照的季节性大幅波动相关的选择压力可能解释了这种突然的遗传间断。我们推断，来自更南部地区的宿主幼虫携带的格氏共生藻基因型会迅速被适应更温和环境的基因型所取代。格氏共生藻强烈的种群结构与波动的环境条件相对应，这表明这些遗传多样的种群有可能迅速进化以适应不断变化的环境，并揭示了极端环境在推动海洋生态系统中微生物真核生物（如浮游生物）物种形成方面的重要性。
