Phylogeny of Kinorhyncha Based on Morphology and Two Molecular Loci

PLoS One. 2015 Jul 22;10(7):e0133440. doi: 10.1371/journal.pone.0133440. eCollection 2015.

Abstract

The phylogeny of Kinorhyncha was analyzed using morphology and the molecular loci 18S rRNA and 28S rRNA. The different datasets were analyzed separately and in combination, using maximum likelihood and Bayesian Inference. Bayesian inference of molecular sequence data in combination with morphology supported the division of Kinorhyncha into two major clades: Cyclorhagida comb. nov. and Allomalorhagida nom. nov. The latter clade represents a new kinorhynch class, and accommodates Dracoderes, Franciscideres, a yet undescribed genus which is closely related with Franciscideres, and the traditional homalorhagid genera. Homalorhagid monophyly was not supported by any analyses with molecular sequence data included. Analysis of the combined molecular and morphological data furthermore supported a cyclorhagid clade which included all traditional cyclorhagid taxa, except Dracoderes that no longer should be considered a cyclorhagid genus. Accordingly, Cyclorhagida is divided into three main lineages: Echinoderidae, Campyloderidae, and a large clade, 'Kentrorhagata', which except for species of Campyloderes, includes all species with a midterminal spine present in adult individuals. Maximum likelihood analysis of the combined datasets produced a rather unresolved tree that was not regarded in the following discussion. Results of the analyses with only molecular sequence data included were incongruent at different points. However, common for all analyses was the support of several major clades, i.e., Campyloderidae, Kentrorhagata, Echinoderidae, Dracoderidae, Pycnophyidae, and a clade with Paracentrophyes + New Genus and Franciscideres (in those analyses where the latter was included). All molecular analyses including 18S rRNA sequence data furthermore supported monophyly of Allomalorhagida. Cyclorhagid monophyly was only supported in analyses of combined 18S rRNA and 28S rRNA (both ML and BI), and only in a restricted dataset where taxa with incomplete information from 28S rRNA had been omitted. Analysis of the morphological data produced results that were similar with those from the combined molecular and morphological analysis. E.g., the morphological data also supported exclusion of Dracoderes from Cyclorhagida. The main differences between the morphological analysis and analyses based on the combined datasets include: 1) Homalorhagida appears as monophyletic in the morphological tree only, 2) the morphological analyses position Franciscideres and the new genus within Cyclorhagida near Zelinkaderidae and Cateriidae, whereas analyses including molecular data place the two genera inside Allomalorhagida, and 3) species of Campyloderes appear in a basal trichotomy within Kentrorhagata in the morphological tree, whereas analysis of the combined datasets places species of Campyloderes as a sister clade to Echinoderidae and Kentrorhagata.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Genetic Loci*
  • Invertebrates / classification
  • Invertebrates / genetics*
  • Phylogeny*
  • RNA, Ribosomal, 18S / genetics*
  • RNA, Ribosomal, 28S / genetics*

Substances

  • RNA, Ribosomal, 18S
  • RNA, Ribosomal, 28S

Grants and funding

This work was supported by The Danish Council for Independent Research | Natural Sciences (http://ufm.dk/en Grant no: 21-04-0331 to MVS—collecting and sequencing of specimens), The Carlsberg Foundation (http://www.carlsbergfondet.dk/ Grants no: 2011_01_0048 and 2013-01-0035 to MVS—collecting and sequencing of specimens), Korean Institute of Ocean Science and Technology (http://eng.kiost.ac/kordi_eng/main/ Grant no. PE99318 and PO01135 to HSR—collecting and sequencing of specimens), "International Research Hub Project for Climate Change and Coral Reef/Island Dynamics from the University of the Ryukyus" and "grant for cultivation of young scientists from the Research Institute of Marine Invertebrate" (to HY—collecting and sequencing of specimens), Spanish Ministry of Science and Technology (http://www.csic.es/ Grant no CGL 2009-08928 to FP—collecting of specimens), and Association of European Marine Biological Laboratories (http://www.assemblemarine.org/access-rules/ to FP, MH, and NS—collecting of specimens).