A stable phylogenomic classification of Travunioidea (Arachnida, Opiliones, Laniatores) based on sequence capture of ultraconserved elements

Molecular phylogenetics has transitioned into the phylogenomic era, with data derived from next-generation sequencing technologies allowing unprecedented phylogenetic resolution in all animal groups, including understudied invertebrate taxa. Within the most diverse harvestmen suborder, Laniatores, most relationships at all taxonomic levels have yet to be explored from a phylogenomics perspective. Travunioidea is an early-diverging lineage of laniatorean harvestmen with a Laurasian distribution, with species distributed in eastern Asia, eastern and western North America, and south-central Europe. This clade has had a challenging taxonomic history, but the current classification consists of ~77 species in three families, the Travuniidae, Paranonychidae, and Nippononychidae. Travunioidea classification has traditionally been based on structure of the tarsal claws of the hind legs. However, it is now clear that tarsal claw structure is a poor taxonomic character due to homoplasy at all taxonomic levels. Here, we utilize DNA sequences derived from capture of ultraconserved elements (UCEs) to reconstruct travunioid relationships. Data matrices consisting of 317–677 loci were used in maximum likelihood, Bayesian, and species tree analyses. Resulting phylogenies recover four consistent and highly supported clades; the phylogenetic position and taxonomic status of the enigmatic genus Yuria is less certain. Based on the resulting phylogenies, a revision of Travunioidea is proposed, now consisting of the Travuniidae, Cladonychiidae, Paranonychidae (Nippononychidae is synonymized), and the new family Cryptomastridae Derkarabetian & Hedin, fam. n., diagnosed here. The phylogenetic utility and diagnostic features of the intestinal complex and male genitalia are discussed in light of phylogenomic results, and the inappropriateness of the tarsal claw in diagnosing higher-level taxa is further corroborated.

分子系统发育学已迈入系统发育组学时代，下一代测序技术产生的数据使得包括研究不足的无脊椎动物类群在内的所有动物类群获得了前所未有的系统发育分辨率。在物种多样性最高的盲蛛强肢亚目（Laniatores）中，各分类层级的多数系统发育关系尚未从系统发育组学视角展开研究。特拉夫盲蛛总科（Travunioidea）是一类早期分化的强肢亚目盲蛛支系，具有劳亚古陆分布格局，其物种分布于东亚、北美东西部以及欧洲中南部。该支系的分类历史较为复杂，现行分类系统将其划分为3个科、约77个物种，分别为特拉夫盲蛛科（Travuniidae）、副爪盲蛛科（Paranonychidae）和日本爪盲蛛科（Nippononychidae）。传统上，特拉夫盲蛛总科的分类依据为后足跗爪的结构，但目前已明确，由于在所有分类层级均存在同塑现象，跗爪结构并非可靠的分类学性状。本研究利用通过超保守元件（ultraconserved elements, UCEs）捕获得到的DNA序列，重建了特拉夫盲蛛总科的系统发育关系：采用包含317至677个基因座的数据矩阵，分别开展最大似然法、贝叶斯法及物种树分析。重建的系统发育树共恢复出4个一致性极高且支持度显著的支系；但神秘属Yuria的系统发育位置及分类地位尚不明确。基于本研究得到的系统发育结果，我们提出特拉夫盲蛛总科的分类修订方案：该总科如今包含特拉夫盲蛛科、枝爪盲蛛科（Cladonychiidae）、副爪盲蛛科（日本爪盲蛛科被归并为异名），以及本文新建立的隐盲蛛科（Cryptomastridae Derkarabetian & Hedin, fam. n.），并在此给出该新科的鉴别特征。此外，本文结合系统发育组学结果讨论了肠道复合体与雄性外生殖器的系统发育适用性，并进一步证实了跗爪作为高级阶元分类特征的不适切性。