Department of Biological Science, Florida State University, Tallahassee, Florida, USA.
Daniel P. Haerther Center for Conservation and Research, John G. Shedd Aquarium, Chicago, Illinois, USA.
Mol Ecol. 2022 Oct;31(20):5368-5385. doi: 10.1111/mec.16654. Epub 2022 Aug 29.
The congruence between phylogenies of tightly associated groups of organisms (cophylogeny) reflects evolutionary links between ecologically important interactions. However, despite being a classic example of an obligate symbiosis, tests of cophylogeny between scleractinian corals and their photosynthetic algal symbionts have been hampered in the past because both corals and algae contain genetically unresolved and morphologically cryptic species. Here, we studied co-occurring, cryptic Pocillopora species from Mo'orea, French Polynesia, that differ in their relative abundance across depth. We constructed new phylogenies of the host Pocillopora (using complete mitochondrial genomes, genomic loci, and thousands of single nucleotide polymorphisms) and their Symbiodiniaceae symbionts (using ITS2 and psbA markers) and tested for cophylogeny. The analysis supported the presence of five Pocillopora species on the fore reef at Mo'orea that mostly hosted either Cladocopium latusorum or C. pacificum. Only Pocillopora species hosting C. latusorum also hosted taxa from Symbiodinium and Durusdinium. In general, the Cladocopium phylogeny mirrored the Pocillopora phylogeny. Within Cladocopium species, lineages also differed in their associations with Pocillopora haplotypes, except those showing evidence of nuclear introgression, and with depth in the two most common Pocillopora species. We also found evidence for a new Pocillopora species (haplotype 10), that has so far only been sampled from French Polynesia, that warrants formal identification. The linked phylogenies of these Pocillopora and Cladocopium species and lineages suggest that symbiont speciation is driven by niche diversification in the host, but there is still evidence for symbiont flexibility in some cases.
紧密相关的生物体群（共进化）的系统发育之间的一致性反映了生态重要相互作用之间的进化联系。然而，尽管珊瑚虫和它们的光合藻类共生体是一种典型的专性共生体，但过去对珊瑚虫和它们的光合藻类共生体之间的共进化的测试一直受到阻碍，因为珊瑚虫和藻类都包含遗传上未解决的和形态上隐蔽的物种。在这里，我们研究了来自法属波利尼西亚莫雷阿岛的共生共栖的隐生珊瑚虫物种，这些物种在深度上的相对丰度不同。我们构建了宿主珊瑚虫（使用完整的线粒体基因组、基因组位点和数千个单核苷酸多态性）及其共生藻（使用 ITS2 和 psbA 标记）的新系统发育，并测试了共进化。分析支持莫雷阿岛前礁上存在五种主要宿主为 Cladocopium latusorum 或 C. pacificum 的珊瑚虫。只有宿主 Cladocopium latusorum 的 Pocillopora 物种也宿主来自 Symbiodinium 和 Durusdinium 的分类群。一般来说，Cladocopium 的系统发育反映了 Pocillopora 的系统发育。在 Cladocopium 物种内，谱系也因与 Pocillopora 单倍型的关系不同而不同，除了那些显示核基因渗入证据的谱系，以及与两种最常见的 Pocillopora 物种的深度不同。我们还发现了一种新的 Pocillopora 物种（单倍型 10）的证据，该物种迄今为止仅在法属波利尼西亚采样，需要正式鉴定。这些 Pocillopora 和 Cladocopium 物种和谱系的连锁系统发育表明，共生体的物种形成是由宿主的生态位多样化驱动的，但在某些情况下仍有共生体灵活性的证据。
