Understanding the diversity and phylogenetic placements of New Zealand amphipods within a global context

Amphipods are an ecologically diverse group of crustaceans. Due to the limited number of fossil data and common morphological homoplasy, molecular data can be very useful to understand their evolutionary relationships and history. However, despite their global distribution and an increasing number of phylogenetic studies, molecular data from the Southern Hemisphere is considerably limited. Here, I report multigene data (18S, 28S, and COI) of New Zealand endemic freshwater families as well as some other marine taxa. Also, I report two new species/genera that have not been described yet. Phylogenetic analyses were conducted including major amphipod groups to understand phylogenetic placements of New Zealand amphipods. Based on the ML and Bayesian trees, <i>Paracallipe</i>, <i>Paraleptamphopus</i>, and the two unknown species belong to the eusiroids/iphimedioids clade; <i>Parorchestia</i> and a talitrid species clearly belong to talitroids; <i>Paracorophium</i> and <i>Monocorophium</i> were placed within corophiids; <i>Themisto</i> belongs to physosomatans; <i>Josephosella</i> was closely related to other hadzoids. The present study suggests that the Southern and Northern Hemisphere freshwater amphipods are likely to have originated from different marine ancestors. Molecular data from other regions in the Southern Hemisphere will be highly valuable for understanding the phylogeographic histories of amphipods that have shaped the current diversity and distribution.

端足类（Amphipods）是一类生态多样性极为丰富的甲壳动物类群。鉴于化石数据稀缺且普遍存在形态趋同演化现象，分子数据对解析其演化关系与演化历史具有关键参考价值。然而，尽管端足类全球广布且相关系统发育研究与日俱增，但南半球的分子数据仍极为匮乏。本研究报道了新西兰特有淡水端足类各科及部分海洋类群的多基因数据（18S、28S及COI基因），同时还报道了两个尚未正式发表描述的新物种与新属。本研究纳入主要端足类类群开展系统发育分析，以明确新西兰端足类的系统发育归属。基于最大似然树与贝叶斯推断树的分析结果：*Paracallipe*、*Paraleptamphopus* 以及两个未知物种隶属于真虾钩虾总科/阿毛钩虾总科支系；*Parorchestia* 与一种跳钩虾类群明确归属于跳钩虾总科支系；*Paracorophium* 与 *Monocorophium* 被置于蜾蠃蜚科类群中；*Themisto* 隶属于体钩虾类；*Josephosella* 与其他哈茨钩虾类群亲缘关系密切。本研究显示，南半球与北半球的淡水端足类可能起源于不同的海洋祖先类群。南半球其他区域的分子数据，对于解析塑造端足类现有多样性与分布格局的系统生物地理学历史具有重要意义。