Phylogenomics reveals deep relationships and diversification within phylactolaemate bryozoans

Bryozoans are mostly sessile colonial invertebrates that inhabit all kinds of aquatic ecosystems. Extant bryozoan species fall into two clades with one of them, Phylactolaemata, being the only exclusively freshwater clade. Phylogenetic relationships within the class Phylactolaemata have long been controversial owing to their limited distinguishable characteristics that reflect evolutionary relationships. Here, we present the first phylogenomic analysis of Phylactolaemata using transcriptomic data combined with dense taxon sampling of six families to better resolve the interrelationships and to estimate divergence time. Using maximum likelihood and Bayesian inference approaches, we recovered a robust phylogeny for Phylactolaemata in which the interfamilial relationships are fully resolved. We show Stephanellidae is the sister taxon of all other phylactolaemates and confirm that Lophopodidae represents the second offshoot within the phylactolaemate tree. Plumatella fruticosa clearly falls...苔藓动物（Bryozoans）多为固着生活的群居无脊椎动物，栖息于各类水生生态系统中。现生苔藓动物物种可划分为两个演化支，其中被唇纲（Phylactolaemata）是唯一的纯淡水演化支。长期以来，由于反映演化关系的可识别特征有限，被唇纲内部的系统发育关系一直存在争议。本研究首次利用转录组数据结合6个科的高密度类群采样，开展被唇纲的系统发育组学分析，以更好地解析其类群间的系统发育关系并估算分化时间。本研究采用最大似然法与贝叶斯推断法，获得了被唇纲高支持度的系统发育树，其科间关系已完全解析。结果显示，羽苔虫科（Stephanellidae）为其他所有被唇纲类群的姊妹群，同时证实冠苔虫科（Lophopodidae）是被唇纲演化树中的第二个演化分支。丛生羽苔虫（Plumatella fruticosa）明确隶属于……