Nuclear genomic signals of the \"microturbellarian\" roots of platyhelminth evolutionary innovation

Flatworms number among the most diverse invertebrate phyla, and represent the most biomedically significant branch of the major bilaterian clade Spiralia, but to date, deep evolutionary relationships within this group have been studied using only a single locus (the rRNA operon), leaving the origins of many key clades unclear. Here, using a survey of genomes and transcriptomes representing all free-living flatworm orders, we provide resolution of platyhelminth interrelationships based on hundreds of nuclear protein-coding genes, exploring phylogenetic signal through concatenation as well as recently developed consensus approaches. These analyses robustly support a modern hypothesis of flatworm phylogeny, one which emphasizes the primacy of the often-overlooked 'microturbellarian' groups in understanding the major evolutionary transitions within Platyhelminthes: perhaps most notably, we propose a novel scenario for the interrelationships between free-living and vertebrate-parasitic flatw...

扁形动物（Flatworms）是物种多样性最为丰富的无脊椎动物类群之一，同时也是大型两侧对称类群螺旋动物（Spiralia）中生物医学研究价值最高的分支。但截至目前，针对该类群内部的深度演化关系，学界仅依托单一位点（核糖体RNA操纵子，rRNA operon）开展过研究，致使诸多关键类群的起源仍未明确。本研究通过对覆盖所有自由生活扁形动物目级类群的基因组与转录组数据进行系统调研，基于数百个核编码蛋白质基因（nuclear protein-coding genes）解析了扁形动物门（Platyhelminthes）的类群间演化关系；分析过程中同时采用了串联法（concatenation）以及近年新兴的共识分析方法（consensus approaches）来探索系统发育信号（phylogenetic signal）。本研究的分析结果稳健地支持了现行的扁形动物系统发育假说——该假说强调常被忽视的微涡虫类（microturbellarian）类群，是理解扁形动物门内主要演化过渡事件的核心；尤为关键的是，我们针对自由生活类群与脊椎动物寄生扁形动物之间的演化关系提出了全新的演化场景。