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Systematics, phylogeny and biogeography
RESEARCH ARTICLE

New insights into the phylogeny, systematics and DNA barcoding of Nemertea

Sebastian Kvist A C , Christopher E. Laumer A , Juan Junoy B and Gonzalo Giribet A
+ Author Affiliations
- Author Affiliations

A Museum of Comparative Zoology, Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.

B EU_US Marine Biodiversity Research Group, Dpto de Ciencias de la Vida and Instituto Franklin, Universidad de Alcalá, E-28871 Alcalá de Henares, Spain.

C Corresponding author. Email: skvist@fas.harvard.edu

Invertebrate Systematics 28(3) 287-308 https://doi.org/10.1071/IS13061
Submitted: 6 December 2013  Accepted: 5 February 2014   Published: 30 June 2014

Abstract

Although some clades of ribbon worms (phylum Nemertea) are consistently recovered with high support in molecular phylogenies, the placement and inter-relationships of some taxa have proven problematic. Herein, we performed molecular phylogenetic analyses aimed at resolving these recalcitrant splits, using six loci (nuclear 18S rRNA, 28S rRNA, histones H3 and H4, and mitochondrial 16S rRNA and COI) for 133 terminals, with particular emphasis on the problematic families Hubrechtidae and Plectonemertidae. Three different datasets were used for phylogenetic analyses and both maximum likelihood and maximum parsimony methodologies were applied. All but one of the resulting tree topologies agree on the paraphyly of the class Palaeonemertea, whereas Heteronemertea, Hoplonemertea, Polystilifera, Monostilifera and Hubrechtidae are always recovered as reciprocally monophyletic. Hubrechtidae is sister group to Heteronemertea (the Pilidiophora hypothesis) only when length variable regions of 18S rRNA and 28S rRNA are excluded. Moreover, the terrestrial and freshwater family Plectonemertidae is recovered with high support and the implications of this finding are further discussed. Finally, we evaluate the utility of DNA barcoding for specimen identification within Nemertea using an extended dataset containing 394 COI sequences. Results suggest that DNA barcoding may work for Nemertea, insofar as a distinct barcoding gap (the gap between the maximum intraspecific variation and the minimum interspecific divergence) may exist, but its recognition is regularly hampered by low accuracy in species level identifications.

Additional keywords: cytochrome c oxidase subunit I, Hubrechtidae, Plectonemertidae, Pilidiophora.


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