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机制，使其能够在这类极端低光照生态系统中存续并占据优势。本研究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）展开宿主-共生体关系分析，样本由载人潜水器在65–125米的深度梯度上采集获得。研究采用三类不同的分子标记对珊瑚与虫黄藻属（Symbiodinium）的基因型进行比较分析，包括珊瑚的COX1-1-rRNA内含子标记、虫黄藻的线粒体细胞色素氧化酶亚基I（COI）标记以及细胞核内部转录间隔区2（ITS2）序列。系统发育重构分析清晰分辨出5种薄孔珊瑚属物种，其中夏威夷薄孔珊瑚（Leptoseris hawaiiensis）仅分布于115–125米的较深生境中。虫黄藻的线粒体标记在C进化枝中鉴定出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，其中一种单倍型仅存在于中光层下限极端生境（95–125米）中。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，这意味着生态位特化在中光层极端生境的宿主-共生体协同演化过程中发挥着关键作用。