Data from: Molecular phylogeny and dating reveal a terrestrial origin in the early Carboniferous for ascaridoid nematodes

Ascaridoids are among the commonest groups of zooparasitic nematodes (roundworms) and occur in the alimentary canal of all major vertebrate groups, including man. They have an extremely high diversity and are of major socio-economic importance. However, their evolutionary history remains poorly known. Here we performed a comprehensive phylogenetic analysis of the Ascaridoidea. Our results divided the Ascaridoidea into six monophyletic major clades, i.e. the Heterocheilidae, Acanthocheilidae, Anisakidae, Ascarididae, Toxocaridae and Raphidascarididae, among which the Heterocheilidae, rather than the Acanthocheilidae, represents the sister clade to the remaining ascaridoids. The phylogeny was calibrated using an approach that involves time priors from fossils of the co-evolving hosts, and dates the common ancestor of the Ascaridoidea back to the Early Carboniferous (approximately 360.47–325.27 Ma). The divergence dates and ancestral host types indicated by our study suggest that members of the Ascaridoidea first parasitized terrestrial tetrapods and subsequently extended their host range to elasmobranchs and teleosts. We also propose that the fundamental terrestrial-aquatic switches of these nematodes were affected by changes in sea-level during the Triassic to the Early Cretaceous.

蛔总科类群（Ascaridoidea）是最为常见的动物寄生性线虫（圆虫）类群之一，可寄生于包括人类在内的所有主要脊椎动物类群的消化道中。它们具有极高的物种多样性，且具备重要的社会经济价值。然而，其演化历史迄今仍鲜为人知。本研究对蛔总科开展了全面的系统发育分析，研究结果将蛔总科划分为6个单系主要演化支，分别为异尾科（Heterocheilidae）、棘唇科（Acanthocheilidae）、异尖科（Anisakidae）、蛔科（Ascarididae）、弓首科（Toxocaridae）以及针蛔科（Raphidascarididae）；其中异尾科而非棘唇科，构成了其余蛔总科类群的姊妹演化支。本研究采用基于协同演化宿主化石的时间先验校准方法对该系统发育树进行定年，结果显示蛔总科的共同祖先可追溯至石炭纪早期（约360.47–325.27 Ma）。本研究揭示的分化时间与祖先宿主类型表明，蛔总科类群最初寄生于陆生四足动物，随后将宿主范围拓展至软骨鱼纲与硬骨鱼纲。本研究同时提出，这些线虫的核心陆生-水生宿主转换事件，受三叠纪至早白垩世期间海平面变化的影响。