Data from: Mitochondrial DNA (COI) analyses reveal that amphipod diversity is associated with environmental heterogeneity in deep-sea habitats

The relationship between species diversity and environmental parameters is poorly understood for the mobile macrofauna of deep-sea habitats due to under-sampling and subsequent lack of accurate taxonomic information. To redress this, cytochrome oxidase c subunit I (COI) DNA sequences were used to estimate species diversity and to compare phoxocephalid amphipod assemblages among 20 stations encompassing a range of environmental conditions. Two regions, east (Chatham Rise) and west (Challenger Plateau) of New Zealand were sampled to depths of 200 – 1200 m with an epibenthic sled. Using a comparison among identified morphospecies, we found a clear gap in sequence divergences between 6 and 13% and used a 6% threshold to designate molecular operational taxonomic units (MOTUs), as a surrogate to putative species. DNA sequences (n=297) revealed high total diversity (n=49 MOTUs), as well as high beta diversity (28 MOTUs found at single location only). Novel phoxocephalid MOTUs were found at most stations, especially on Challenger Plateau and the flanks of Chatham Rise. Analyses of inter-station assemblages revealed a major split between regions, indicating minimal overlap in taxon distributions. A cluster of highly similar stations was identified, broadly distributed over the crest of Chatham Rise, in association with elevated food availability, probably resulting from higher surface productivity and relatively shallow depth. Accordingly, multivariate analysis revealed a strong correlation between phoxocephalid assemblages and food supply. This study highlights the value of molecular approaches, in particular COI sequences, for quantifying and comparing diversity in under-sampled and/or under-studied taxa.由于采样不足且后续缺乏准确的分类学信息，学界对深海生境中的移动型大型底栖生物（mobile macrofauna）的物种多样性与环境参数之间的关联仍知之甚少。为弥补这一研究空白，本研究采用细胞色素c氧化酶亚基I（cytochrome oxidase c subunit I, COI）的DNA序列，估算物种多样性，并对比了覆盖多种环境条件的20个采样站位中的蜾蠃蜚科端足类（phoxocephalid amphipod）集合群落组成。研究采样覆盖新西兰东侧的查塔姆海隆（Chatham Rise）与西侧的挑战者高原（Challenger Plateau）两个区域，采样深度范围为200~1200米，采用底表拖网（epibenthic sled）进行采样。通过与已鉴定的形态种（morphospecies）进行对比，研究团队发现序列分歧度在6%~13%之间存在显著分界，并采用6%的阈值界定分子操作分类单元（molecular operational taxonomic units, MOTUs），以此作为推定物种的替代指标。对297条DNA序列的分析显示，整体物种多样性较高（共得到49个MOTUs），同时β多样性（beta diversity）也处于较高水平——其中28个MOTUs仅在单个采样站位被发现。多数采样站位均发现了新的蜾蠃蜚科端足类MOTUs，其中以挑战者高原及查塔姆海隆侧翼的检出数量尤为突出。对站位间集合群落的分析显示，两个区域的类群组成存在显著分化，表明类群分布的重叠度极低。研究团队还识别出一组高度相似的采样站位，广泛分布于查塔姆海隆的脊部区域，这些站位的食物供给水平较高，这可能源于更高的表层海洋生产力以及相对较浅的采样深度。据此，多变量分析结果显示，蜾蠃蜚科端足类的集合群落组成与食物供给水平之间存在显著相关性。本研究凸显了分子生物学方法——尤其是COI序列——在量化和对比采样不足及/或研究不足的类群多样性方面的应用价值。