Matias Ambrocio Melvin A, Popovic Iva, Thia Joshua A, Cooke Ira R, Torda Gergely, Lukoschek Vimoksalehi, Bay Line K, Kim Sun W, Riginos Cynthia
Institute of Biology University of the Philippines Diliman Quezon City Philippines.
School of Biological Sciences The University of Queensland St. Lucia Queensland Australia.
Evol Appl. 2022 Jul 7;16(2):293-310. doi: 10.1111/eva.13435. eCollection 2023 Feb.
Genomic studies are uncovering extensive cryptic diversity within reef-building corals, suggesting that evolutionarily and ecologically relevant diversity is highly underestimated in the very organisms that structure coral reefs. Furthermore, endosymbiotic algae within coral host species can confer adaptive responses to environmental stress and may represent additional axes of coral genetic variation that are not constrained by taxonomic divergence of the cnidarian host. Here, we examine genetic variation in a common and widespread, reef-building coral, , and its associated endosymbiotic algae along the entire expanse of the Great Barrier Reef (GBR). We use SNPs derived from genome-wide sequencing to characterize the cnidarian coral host and organelles from zooxanthellate endosymbionts (genus ). We discover three distinct and sympatric genetic clusters of coral hosts, whose distributions appear associated with latitude and inshore-offshore reef position. Demographic modelling suggests that the divergence history of the three distinct host taxa ranges from 0.5 to 1.5 million years ago, preceding the GBR's formation, and has been characterized by low-to-moderate ongoing inter-taxon gene flow, consistent with occasional hybridization and introgression typifying coral evolution. Despite this differentiation in the cnidarian host, taxa share a common symbiont pool, dominated by the genus (Clade C). plastid diversity is not strongly associated with host identity but varies with reef location relative to shore: inshore colonies contain lower symbiont diversity on average but have greater differences between colonies as compared with symbiont communities from offshore colonies. Spatial genetic patterns of symbiont communities could reflect local selective pressures maintaining coral holobiont differentiation across an inshore-offshore environmental gradient. The strong influence of environment (but not host identity) on symbiont community composition supports the notion that symbiont community composition responds to habitat and may assist in the adaptation of corals to future environmental change.
基因组研究正在揭示造礁珊瑚内部广泛存在的隐秘多样性，这表明在构建珊瑚礁的生物中，具有进化和生态相关性的多样性被严重低估了。此外，珊瑚宿主物种内的内共生藻类可以赋予对环境压力的适应性反应，并且可能代表珊瑚遗传变异的额外维度，而这些维度不受刺胞动物宿主分类差异的限制。在这里，我们沿着大堡礁（GBR）的整个区域，研究了一种常见且分布广泛的造礁珊瑚及其相关的内共生藻类的遗传变异。我们使用来自全基因组测序的单核苷酸多态性（SNPs）来表征刺胞动物珊瑚宿主以及虫黄藻内共生体（属）的细胞器。我们发现了珊瑚宿主的三个不同且同域的遗传簇，它们的分布似乎与纬度和近岸-离岸珊瑚礁位置相关。种群动态建模表明，这三个不同宿主类群的分化历史可追溯到0.5至150万年前，早于大堡礁的形成，其特征是类群间持续存在低到中等程度的基因流动，这与典型的珊瑚进化中偶尔的杂交和基因渗入一致。尽管刺胞动物宿主存在这种分化，但类群共享一个共同的共生体库，以属（进化枝C）为主导。共生体的质体多样性与宿主身份没有强烈关联，但随相对于海岸的珊瑚礁位置而变化：近岸群体平均包含较低的共生体多样性，但与离岸群体的共生体群落相比，群体之间的差异更大。共生体群落的空间遗传模式可能反映了维持珊瑚全生物在近岸-离岸环境梯度上分化的局部选择压力。环境（而非宿主身份）对共生体群落组成的强烈影响支持了这样一种观点，即共生体群落组成对栖息地有反应，并且可能有助于珊瑚适应未来的环境变化。
