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.栖息于中光层生境（mesophotic habitat）下限的珊瑚，大概率拥有独特的光合适应策略，使其能够在这类极端低光照生态系统中存续并占据优势。我们针对夏威夷海域中光层环境中的优势珊瑚属——薄孔珊瑚属（Leptoseris）的宿主-共生体关系展开研究，样本由潜水器在65至125米的深度梯度范围内采集获得。我们采用三类不同的分子标记对珊瑚与虫黄藻（Symbiodinium）的基因型进行对比分析，标记分别为珊瑚的（COX1–1-rRNA 内含子）、虫黄藻的线粒体标记COI，以及细胞核ITS2序列。系统发育重建清晰地鉴定出5种薄孔珊瑚，其中夏威夷薄孔珊瑚（Leptoseris hawaiiensis）仅在115至125米的深水区被发现。虫黄藻的线粒体标记在C进化支中鉴定出3种明确的单倍型，这些单倍型在不同宿主物种与不同深度的分布频率存在显著差异，其中1种单倍型仅存在于中光层的极端下限区域（95至125米）。这类宿主-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，这暗示生态位特化在中光层极端环境下的宿主-共生体演化过程中发挥着关键作用。