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- Rousset, V., et al.
(författare)
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A molecular phylogeny of annelids
- 2007
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Ingår i: Cladistics. - : Wiley. - 0748-3007 .- 1096-0031. ; 23:1, s. 41-63
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Tidskriftsartikel (refereegranskat)abstract
- We present parsimony analyses of annelids based on the largest taxon sample and most extensive molecular data set yet assembled, with two nuclear ribosomal genes (18S rDNA and the D1 region of 28S rDNA), one nuclear protein coding-gene (Histone H3) and one mitochondrial ribosomal gene (16S rDNA) from 217 terminal taxa. Of these, 267 sequences are newly sequenced, and the remaining were obtained from GenBank. The included taxa are based on the criteria that the taxon must have 18S rDNA or at least two other loci. Our analyses show that 68% of annelid family ranked taxa represented by more than one taxon in our study are supported by a jackknife value > 50%. In spite of the size of our data set, the phylogenetic signal in the deepest part of the tree remains weak and the majority of the currently recognized major polychaete clades (except Amphinomida and Aphroditiformia) could not be recovered. Terbelliformia is monophyletic (with the exclusion of Pectinariidae, for which only 18S data were available), whereas members of taxa such as Phyllodocida, Cirratuliformia, Sabellida and Scolecida are scattered over the trees. Clitellata is monophyletic, although Dinophilidae should possibly be included, and Clitellata has a sister group within the polychaetes. One major problem is the current lack of knowledge on the closest relatives to annelids and the position of the annelid root. We suggest that the poor resolution in the basal parts of the trees presented here may be due to lack of signal connected to incomplete data sets both in terms of terminal and gene sampling, rapid radiation events and/or uneven evolutionary rates and long-branch attraction.
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- Rousset, V, et al.
(författare)
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Evolution for habitat preference in Clitellata (Annelida)
- 2008
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 95:3, s. 447-464
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Tidskriftsartikel (refereegranskat)abstract
- Clitellata (earthworms, leeches, and allies) is a clade of segmented annelid worms that comprise more than 5000 species found worldwide in many aquatic and terrestrial habitats. According to current views, the first clitellates were either aquatic (marine or freshwater) or terrestrial. To address this question further, we assessed the phylogenetic relationships among clitellates using parsimony, maximum likelihood and Bayesian analyses of 175 annelid 18S ribosomal DNA sequences. We then defined two ecological characters (Habitat and Aquatic-environment preferences) and mapped those characters on the trees from the three analyses, using parsimony character-state reconstruction (i.e. Fitch optimization). We accommodated phylogenetic uncertainty in the character mapping by reconstructing character evolution on all the trees resulting from parsimony and maximum likelihood bootstrap analyses and, in the Bayesian inference, on the trees sampled using the Markov chain Monte Carlo algorithm. Our analyses revealed that an 'aquatic' ancestral state for clitellates is a robust result. By using alterations of coding characters and constrained analyses, we also demonstrated that the hypothesis for a terrestrial origin of clitellates is not supported. Our analyses also suggest that the most recent ancestor of clitellates originated from a freshwater environment. However, we stress the importance of adding sequences of some rare marine taxa to more rigorously assess the freshwater origin of Clitellata.
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