A Transcriptomic-Phylogenomic Analysis of the Evolutionary Relationships of Flatworms

摘要: The interrelationships of the flatworms (phylum Platyhelminthes) are poorly resolved despite decades morphological and molecular phylogenetic studies [1, 2]. earliest-branching clades (Catenulida, Macrostomorpha, Polycladida) share spiral cleavage entolecithal eggs with other lophotrochozoans. Lecithoepitheliata have primitive but derived ectolecithal eggs. Other orders (Rhabdocoela, Proseriata, Tricladida relatives, Bothrioplanida) all uncertain affinities to one another. parasitic Neodermata emerge from an position within these classes. To tackle problems, we sequenced transcriptomes 18 5 metazoan groups. addition published data produces alignment >107,000 amino acids less than 28% missing 27 flatworm taxa in 11 covering major clades. Our analyses show that Platyhelminthes consist two Catenulida Rhabditophora. Within Rhabditophora, earliest-emerging branch is not Polycladida. We members Neoophora sister group Polycladida, implying independent origins found Neoophora. resolve Rhabdocoela as most basally branching euneoophoran taxon. Tricladida, Bothrioplanida, constitute a appears lost both centrosomes. identify Bothrioplanida long-sought closest free-living Neodermata. Among orders, Cestoda closer Trematoda to Monogenea, rejecting concept Cercomeromorpha. results important implications for understanding evolution this phylum.