Polyclad phylogeny persists to be problematic
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ORIGINAL ARTICLE
Polyclad phylogeny persists to be problematic Isabel L. Dittmann 1
&
Daniel Cuadrado 2 & Maria Teresa Aguado 3,4 & Carolina Noreña 2 & Bernhard Egger 1
Received: 12 April 2019 / Accepted: 14 August 2019 # The Author(s) 2019
Abstract Two conflicting morphological approaches to polyclad systematics highlight the relevance of molecular data for resolving the interrelationships of Polycladida. In the present study, phylogenetic trees were reconstructed based on a short alignment of the 28S rDNA marker gene with 118 polyclad terminals (24 new) including 100 different polyclad species from 44 genera and 22 families, as well as on a combined dataset using 18S and 28S rDNA genes with 27 polyclad terminals (19 new) covering 26 different polyclad species. In both approaches, Theamatidae and Cestoplanidae were included, two families that have previously been shown to switch from Acotylea to Cotylea. Three different alignment methods were used, both with and without alignment curation by Gblocks, and all alignments were subjected to Bayesian inference and maximum likelihood tree calculations. Over all trees of the combined dataset, an extended majority-rule consensus tree had weak support for Theamatidae and Cestoplanidae as acotyleans, and also the cotylean genera Boninia, Chromyella and Pericelis appeared as acotyleans. With the most inclusive short 28S dataset, on the other hand, there is good support for the aforementioned taxa as cotyleans. Especially with the short 28S matrix, taxon sampling, outgroup selection, alignment method and curation, as well as model choice were all decisive for tree topology. Well-supported parts of the phylogeny over all trees include Pseudocerotoidea, Prosthiostomoidea, Stylochoidea, Leptoplanoidea and Cryptoceloidea, the latter three with new definitions. Unstable positions in the tree were found not only for Theamatidae, Cestoplanidae, Boninia, Chromyella and Pericelis, but also for Anonymus, Chromoplana and Cycloporus. Keywords Platyhelminthes . Polycladida . Cotylea . Acotylea . Molecular phylogenetics . Systematics
Introduction Due to their colourful appearance, polyclad flatworms are among the most conspicuous members of the phylum Platyhelminthes, yet these animals are relatively poorly Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13127-019-00415-1) contains supplementary material, which is available to authorized users. * Bernhard Egger [email protected] 1
Institute of Zoology, University of Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria
2
Museo Nacional de Ciencias Naturales (CSIC), José Gutiérrez Abascal 2, 28006 Madrid, Spain
3
Animal Evolution and Biodiversity, Johann-Friedrich-Blumenbach Institute for Zoology & Anthropology, Georg-August-Universität Göttingen, Göttingen, Germany
4
Centro de Investigación en Biodiversidad y Cambio Global (CIBC-UAM). Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain
studied (Bahia et al. 2017). Usua
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