Coral-associated bacteria demonstrate phylosymbiosis and cophylogeny

Scleractinian corals microbial symbionts influence host health, yet how these coral microbiomes assembled over evolution is not well understood. We survey bacterial and archaeal communities in phylogenetically diverse Australian corals representing more than 425 million years of diversification. We show that corals exhibit anatomical compartmentalization of the microbiome such that the coral surface mucus layer, tissue, and skeleton microbiomes show distinct modern microbial ecology and evolutionary assembly. In corals, these compartments differ greatly in microbial community composition, richness, and response to host vs. environmental drivers. We also find evidence of coral-microbe phylosymbiosis, in which coral microbiome composition and richness reflects coral phylogeny. Surprisingly, the coral skeleton represents the most biodiverse coral microbiome, and also shows the strongest evidence of phylosymbiosis. Together these results trace microbial symbiosis across anatomy during the evolution of a basal animal lineage.

石珊瑚目珊瑚（Scleractinian corals）的微生物共生体可影响宿主健康，但目前学界对这些珊瑚微生物组的演化组装机制仍知之甚少。本研究对系统发育多样性各异的澳大利亚珊瑚中的细菌与古菌群落展开调研，这些珊瑚的演化分化时长已超4.25亿年。研究发现，珊瑚的微生物组呈现解剖学分区特征：珊瑚表面黏液层、组织与骨骼的微生物组，在现代微生物生态学特征与演化组装模式上均存在显著差异。在珊瑚体内，这些分区的微生物群落组成、丰富度，以及对宿主与环境驱动因子的响应模式均存在显著差异。本研究还发现了珊瑚-微生物系统发育共生（phylosymbiosis）的证据：珊瑚微生物组的组成与丰富度能够反映珊瑚自身的系统发育关系。令人意外的是，珊瑚骨骼是所有珊瑚微生物组中生物多样性最高的组分，同时也展现出最强的系统发育共生信号。综上，本研究结果揭示了基底动物类群演化过程中，微生物共生关系沿解剖学分区的分布特征。