title: Phylogenetic position of Myriapoda revealed by 454 transcriptome sequencing.
abstract: Myriapods had been considered closely allied to hexapods (insects and relatives). However, analyses of molecular sequence data have consistently placed Myriapoda either as a sister group of Pancrustacea, comprising crustaceans and hexapods, and thereby supporting the monophyly of Mandibulata, or retrieved Myriapoda as a sister group of Chelicerata (spiders, ticks, mites and allies). In addition, the relationships among the four myriapod groups (Pauropoda, Symphyla, Diplopoda, Chilopoda) are unclear. To resolve the phylogeny of myriapods and their relationship to other main arthropod groups, we collected transcriptome data from the symphylan Symphylella vulgaris, the centipedes Lithobius forficatus and Scolopendra dehaani, and the millipedes Polyxenus lagurus, Glomeris pustulata and Polydesmus angustus by 454 sequencing. We concatenated a multiple sequence alignment that contained 1550 orthologous single copy genes (1,109,847 amino acid positions) from 55 euarthropod and 14 outgroup taxa. The final selected alignment included 181 genes and 37,425 amino acid positions from 55 taxa, with eight myriapods and 33 other euarthropods. Bayesian analyses robustly recovered monophyletic Mandibulata, Pancrustacea and Myriapoda. Most analyses support a sister group relationship of Symphyla in respect to a clade comprising Chilopoda and Diplopoda. Inclusion of additional sequence data from nine myriapod species resulted in an alignment with poor data density, but broader taxon average. With this dataset we inferred Diplopoda+Pauropoda as closest relatives (i.e., Dignatha) and recovered monophyletic Helminthomorpha. Molecular clock calculations suggest an early Cambrian emergence of Myriapoda ∼513 million years ago and a late Cambrian divergence of myriapod classes. This implies a marine origin of the myriapods and independent terrestrialization events during myriapod evolution.
authors.affiliation: Zoologisches Institut & Museum, Biozentrum Grindel, Martin-Luther-King Platz 3, D-20146 Hamburg, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Rehm
authors.affiliation: Zoologisches Forschungsmuseum Alexander Koenig, Zentrum für Molekulare Biodiversitätsforschung (zmb), Adenauerallee 160, D-53113 Bonn, Germany; CSIRO Ecosystem Sciences, Australian National Insect Collection, Clunies Ross Street, Acton, ACT 2601, Australia.
authors.forename: Karen
authors.initials: K
authors.lastname: Meusemann
authors.affiliation: Zoologisches Institut & Museum, Biozentrum Grindel, Martin-Luther-King Platz 3, D-20146 Hamburg, Germany.
authors.forename: Janus
authors.initials: J
authors.lastname: Borner
authors.affiliation: Zoologisches Forschungsmuseum Alexander Koenig, Zentrum für Molekulare Biodiversitätsforschung (zmb), Adenauerallee 160, D-53113 Bonn, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Misof
authors.affiliation: Zoologisches Institut & Museum, Biozentrum Grindel, Martin-Luther-King Platz 3, D-20146 Hamburg, Germany. Electronic address: thorsten.burmester@uni-hamburg.de.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Burmester
mesh_terms: D000818:Animals; D001181:Arthropods / Q000145:classification / Q000235:genetics*; D001499:Bayes Theorem; D056926:CLOCK Proteins / Q000235:genetics; D010802:Phylogeny; D059467:Transcriptome
chemical_list: D056926:CLOCK Proteins
keywords: Arthropoda; Bayesian analyses; Mandibulata; Maximum Likelihood; Myriapoda; Myriochelata