Data from: Molecular signatures of host specificity linked to habitat specialization in Exaiptasia sea anemones.

Rising ocean temperatures associated with global climate change induce breakdown of the symbiosis between coelenterates and photosynthetic microalgae of the genus Symbiodinium. Association with more thermotolerant partners could contribute to resilience, but the genetic mechanisms controlling specificity of hosts for particular Symbiodinium types are poorly known. Here we characterize wild populations of a sea anemone laboratory model system for anthozoan symbiosis, from contrasting environments in Caribbean Panama. Patterns of anemone abundance and symbiont diversity were consistent with specialization of holobionts for particular habitats, with Exaiptasia pallida/S. minutum (ITS2 type B1) abundant on vertical substrate in thermally stable, shaded environments but E. brasiliensis/Symbiodinium sp. (ITS2 clade A) more common in shallow areas subject to high temperature and irradiance. Population genomic sequencing revealed a novel E. pallida population from the Bocas del Toro Archipelago that only harbors S. minutum. Loci most strongly associated with divergence of the Bocas-specific population were enriched in genes with putative roles in cnidarian symbiosis, including activators of the complement pathway of the innate immune system, thrombospondin-type-1 repeat domain proteins, and coordinators of endocytic recycling. Our findings underscore the importance of unmasking cryptic diversity in natural populations and the role of long-term evolutionary history in mediating interactions with Symbiodinium.

伴随全球气候变化而来的海洋温度升高，会诱发刺胞动物（coelenterates）与虫黄藻属（Symbiodinium）光合微藻之间的共生关系破裂。与耐热性更强的共生伙伴建立关联，或许有助于提升宿主的环境适应能力，但目前学界对调控宿主针对特定虫黄藻类型特异性的遗传机制仍知之甚少。本研究对采自巴拿马加勒比海区域不同生境的海葵野生种群进行了系统性特征解析——该海葵是花虫纲（anthozoan）共生研究的经典实验室模型体系。海葵丰度与共生藻多样性的分布模式，与共生功能体针对特定生境的特化现象相符：在温度稳定且遮阴的垂直基质生境中，苍白艾氏海葵（Exaiptasia pallida）/细小虫黄藻（Symbiodinium minutum，ITS2型B1）占优势；而在高温、强光照的浅水区，巴西艾氏海葵（E. brasiliensis）/虫黄藻属物种（Symbiodinium sp.，ITS2演化支A）更为常见。群体基因组测序结果显示，在博卡斯德尔托罗群岛（Bocas del Toro Archipelago）发现了一个全新的苍白艾氏海葵种群，该种群仅携带细小虫黄藻。与博卡斯群岛特有种群分化显著相关的基因位点，显著富集于推测参与刺胞动物共生过程的基因：包括先天免疫系统补体通路激活因子、血小板反应蛋白1型重复结构域蛋白，以及内吞循环调控因子。本研究结果凸显了揭示自然种群隐性多样性的重要性，以及长期演化历史在介导宿主与虫黄藻互作过程中的关键作用。