[Molecular phylogeny of gastrotricha based on 18S rRNA genes comparison: rejection of hypothesis of relatedness with nematodes].
Gastrotrichs are meiobenthic free-living aquatic worms whose phylogenetic and intra-group relationships remain unclear despite some attempts to resolve them on the base of morphology or molecules. In this study we analysed complete sequences of the 18S rRNA gene of 15 taxa (8 new and 7 published) to test numerous hypotheses on gastrotrich phylogeny and to verify whether controversial interrelationships from previous molecular data could be due to the short region available for analysis and the poor taxa sampling. Data were analysed using both maximum likelihood and Bayesian inference. Results obtained suggest that gastrotrichs, together with Gnathostomulida, Plathelminthes, Syndermata (Rotifera + Acanthocephala), Nemertea and Lophotrochozoa, comprise a clade Spiralia. Statistical tests reject phylogenetic hypotheses regarding Gastrotricha as close relatives of Nematoda and other Ecdysozoa or placing them at the base of bilaterian tree close to acoels and nemertodermatides. Within Gastrotricha, Chaetonotida and Macrodasyida comprise two well supported clades. Our analysis confirmed the monophyly of the Chaetonotidae and Xenotrichulidae within Chaetonida as well as Turbanellidae and Thaumastodermatidae within Macrodasyida. Mesodasys is a sister group of the Turbanellidae, and Lepidodasyidae appears to be a polyphyletic group as Cephalodasys forms a separate lineage at the base of macrodasyids, whereas Lepidodasys groups with Neodasys between Thaumastodermatidae and Turbanellidae. To infer a more reliable Gastrotricha phylogeny many species and additional genes should be involved in future analyses.
N B
NB
Petrov
A N
AN
Pegova
O G
OG
Manylov
N S
NS
Vladychenskaia
N S
NS
Miuge
V V
VV
Aleshin
D000818:Animals; D001499:Bayes Theorem; D019143:Evolution, Molecular; D020459:Genes, rRNA; D006376:Helminths / Q000145:classification* / Q000235:genetics; D016013:Likelihood Functions; D009348:Nematoda / Q000145:classification / Q000235:genetics; D010802:Phylogeny; D018510:RNA, Helminth / Q000032:analysis; D012337:RNA, Ribosomal, 18S / Q000032:analysis*
D018510:RNA, Helminth; D012337:RNA, Ribosomal, 18S