Data from: Depth specialization in mesophotic corals (Leptoseris spp.) and associated algal symbionts in Hawai‘i

Corals at the lower limits of mesophotic habitats are likely to have unique photosynthetic adaptations that allow them to persist and dominate in these extreme low light ecosystems. We examined the host–symbiont relationships from the dominant coral genus Leptoseris in mesophotic environments from Hawai'i collected by submersibles across a depth gradient of 65–125 m. Coral and Symbiodinium genotypes were compared with three distinct molecular markers including coral (COX1–1-rRNA intron) and Symbiodinium (COI) mitochondrial markers and nuclear ITS2. The phylogenetic reconstruction clearly resolved five Leptoseris species, including one species (Leptoseris hawaiiensis) exclusively found in deeper habitats (115–125 m). The Symbiodinium mitochondrial marker resolved three unambiguous haplotypes in clade C, which were found at significantly different frequencies between host species and depths, with one haplotype exclusively found at the lower mesophotic extremes (95–125 m). These patterns of host–symbiont depth specialization indicate that there are limits to connectivity between upper and lower mesophotic zones, suggesting that niche specialization plays a critical role in host–symbiont evolution at mesophotic extremes.中光层生境（mesophotic habitat）下限区域的珊瑚，大概率具备独特的光合适应性，使其可在这类极端低光照生态系统中存活并占据优势地位。本研究借助载人深潜器，在夏威夷海域65–125米的深度梯度范围内采集样本，针对中光层环境中的优势珊瑚类群——薄孔珊瑚属（Leptoseris），解析其宿主-共生体（host-symbiont）关系。研究采用三类特异性分子标记对珊瑚与虫黄藻（Symbiodinium）的基因型开展比对分析：包括珊瑚的（COX1–1-rRNA内含子）线粒体标记、虫黄藻的COI线粒体标记，以及细胞核内转录间隔区2（ITS2）。系统发育重建分析清晰区分出五种薄孔珊瑚，其中夏威夷薄孔珊瑚（Leptoseris hawaiiensis）仅分布于115–125米的更深水域。虫黄藻的线粒体标记在C进化支中解析出三种明确的单倍型（haplotype），这些单倍型在不同宿主物种及不同深度的出现频率存在显著差异；其中一种单倍型仅分布于中光层下限极端区域（95–125米）。这种宿主-共生体的深度特化模式表明，中光层上下区域之间的连通性存在限制，这提示生态位特化在中光层极端环境的宿主-共生体演化过程中发挥着关键作用。