Phylogenomics offers resolution of major tunicate relationships

Tunicata, a diverse clade of approximately 3,000 described species of marine, filter-feeding chordates, is of great interest to researchers because tunicates are the closest living relatives of vertebrates and they facilitate comparative studies of our own biology. The group also includes numerous invasive species that cause considerable economic damage and some species of tunicates are edible. Despite their diversity and importance, relationships among major lineages of Tunicata are not completely resolved. Here, we supplemented public data with transcriptomes from seven species spanning the diversity of Tunicata and conducted phylogenomic analyses on data sets of up to 798 genes. Sensitivity analyses were employed to examine the influences of reducing compositional heterogeneity and branch-length heterogeneity. All analyses maximally supported a monophyletic Tunicata within Olfactores (Vertebrata + Tunicata). Within Tunicata, all analyses recovered Appendicularia sister to the rest of...尾索动物亚门（Tunicata）是一类多样性丰富的演化支，目前已描述的海洋滤食性脊索动物约有3000种，因其是现存与脊椎动物亲缘关系最近的类群，且可助力对人类自身生物学开展比较研究，因而备受研究者关注。该类群还包含诸多会造成显著经济损失的入侵物种，部分尾索动物种类还可食用。尽管尾索动物具有丰富的多样性与重要的研究价值，但其主要类群间的演化关系尚未完全厘清。本研究通过新增覆盖尾索动物全部多样性类群的7个物种的转录组数据，补充了公共数据集，并针对最高包含798个基因的数据集开展系统基因组学分析。我们采用敏感性分析，以考察降低组成异质性与支长异质性所带来的影响。所有分析均最大程度支持嗅球动物（Olfactores，脊椎动物+尾索动物）支下的尾索动物亚门为单系群。在尾索动物亚门内部，所有分析均将幼形纲（Appendicularia）恢复为其余类群的姊妹群……