title: Molecular phylogeny of beetle associated diplogastrid nematodes suggests host switching rather than nematode-beetle coevolution.
abstract: BACKGROUND
  Nematodes are putatively the most species-rich animal phylum. They have various life styles and occur in a variety of habitats, ranging from free-living nematodes in aquatic or terrestrial environments to parasites of animals and plants. The rhabditid nematode Caenorhabditis elegans is one of the most important model organisms in modern biology. Pristionchus pacificus of the family of the Diplogastridae has been developed as a satellite model for comparison to C. elegans. The Diplogastridae, a monophyletic clade within the rhabditid nematodes, are frequently associated with beetles. How this beetle-association evolved and whether beetle-nematode coevolution occurred is still elusive. As a prerequisite to answering this question a robust phylogeny of beetle-associated Diplogastridae is needed.
  
  
  RESULTS
  Sequences for the nuclear small subunit ribosomal RNA and for 12 ribosomal protein encoding nucleotide sequences were collected for 14 diplogastrid taxa yielding a dataset of 5996 bp of concatenated aligned sequences. A molecular phylogeny of beetle-associated diplogastrid nematodes was established by various algorithms. Robust subclades could be demonstrated embedded in a phylogenetic tree topology with short internal branches, indicating rapid ancestral divergences. Comparison of the diplogastrid phylogeny to a comprehensive beetle phylogeny revealed no major congruence and thus no evidence for a long-term coevolution.
  
  
  CONCLUSIONS
  Reconstruction of the phylogenetic history of beetle-associated Diplogastridae yields four distinct subclades, whose deep phylogenetic divergence, as indicated by short internal branch lengths, shows evidence for evolution by successions of ancient rapid radiation events. The stem species of the Diplogastridae existed at the same time period when the major radiations of the beetles occurred. Comparison of nematode and beetle phylogenies provides, however, no evidence for long-term coevolution of diplogastrid nematodes and their beetle hosts. Instead, frequent host switching is observed. The molecular phylogeny of the Diplogastridae provides a framework for further examinations of the evolution of these associations, for the study of interactions within the ecosystems, and for investigations of diplogastrid genome evolution.
authors.affiliation: Max Planck Institute for Developmental Biology, Department of Evolutionary Biology, 72076 Tübingen, Germany. werner.mayer@tuebingen.mpg.de
authors.forename: Werner E
authors.initials: WE
authors.lastname: Mayer
authors.forename: Matthias
authors.initials: M
authors.lastname: Herrmann
authors.forename: Ralf J
authors.initials: RJ
authors.lastname: Sommer
mesh_terms: D000465:Algorithms; D000818:Animals; D001499:Bayes Theorem; D001517:Coleoptera / Q000469:parasitology*; D004275:DNA, Ribosomal / Q000235:genetics; D019143:Evolution, Molecular; D020224:Expressed Sequence Tags; D015723:Gene Library; D006790:Host-Parasite Interactions / Q000235:genetics; D009348:Nematoda / Q000145:classification / Q000235:genetics*; D010802:Phylogeny; D012335:RNA, Ribosomal / Q000235:genetics; D012269:Ribosomal Proteins / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D004275:DNA, Ribosomal; D012335:RNA, Ribosomal; D012269:Ribosomal Proteins
references.citation: Curr Biol. 2008 Jan 22;18(2):142-6
references.pmid: 18207741
references.citation: Mol Biol Evol. 1988 Sep;5(5):568-83
references.pmid: 3193878
references.citation: Science. 2007 Dec 21;318(5858):1913-6
references.pmid: 18096805
references.citation: Bioessays. 2006 Jun;28(6):651-9
references.pmid: 16700067
references.citation: Nat Genet. 2008 Oct;40(10):1193-8
references.pmid: 18806794
references.citation: Mol Biol Evol. 1997 Jul;14(7):685-95
references.pmid: 9254330
references.citation: Front Zool. 2006 Sep 12;3:14
references.pmid: 16968539
references.citation: Curr Biol. 2007 Nov 20;17(22):1925-37
references.pmid: 18024125
references.citation: Syst Biol. 2007 Jun;56(3):504-14
references.pmid: 17562474
references.citation: Syst Biol. 2003 Oct;52(5):696-704
references.pmid: 14530136
references.citation: Bioinformatics. 1998;14(9):817-8
references.pmid: 9918953
references.citation: BMC Evol Biol. 2007 Jul 02;7:104
references.pmid: 17605767
references.citation: Bioinformatics. 2003 Aug 12;19(12):1572-4
references.pmid: 12912839
references.citation: Nature. 1998 Mar 5;392(6671):71-5
references.pmid: 9510248
references.citation: Proc Natl Acad Sci U S A. 2008 Aug 5;105(31):10826-31
references.pmid: 18664575
references.citation: Zoolog Sci. 2007 Sep;24(9):883-9
references.pmid: 17960992
references.citation: Nat Rev Genet. 2009 Jun;10(6):416-22
references.pmid: 19369972
references.citation: Zoology (Jena). 2006;109(2):96-108
references.pmid: 16616467
references.citation: Mol Biol Evol. 1987 Jul;4(4):406-25
references.pmid: 3447015
references.citation: Curr Biol. 2006 Jul 25;16(14):1386-94
references.pmid: 16860737
references.citation: Nucleic Acids Res. 2008 Jul 1;36(Web Server issue):W465-9
references.pmid: 18424797
references.citation: Evol Dev. 2008 May-Jun;10(3):273-9
references.pmid: 18460089
references.citation: Genes Dev. 2004 May 15;18(10):1198-208
references.pmid: 15155582
references.citation: Genetics. 1985 Jun;110(2):325-44
references.pmid: 4007484
references.citation: Nucleic Acids Res. 1997 Sep 1;25(17):3389-402
references.pmid: 9254694
references.citation: Curr Biol. 2006 Dec 5;16(23):2359-65
references.pmid: 17141618
references.citation: Mol Ecol. 2002 Apr;11(4):839-50
references.pmid: 11972769
references.citation: Evolution. 1985 Jul;39(4):783-791
references.pmid: 28561359
references.citation: Nucleic Acids Res. 1997 Dec 15;25(24):4876-82
references.pmid: 9396791
references.citation: Mol Biol Evol. 2006 Sep;23(9):1792-800
references.pmid: 16790472
references.citation: J Exp Zool B Mol Dev Evol. 2005 Jan 15;304(1):64-74
references.pmid: 15593277