02786nas a2200193   4500008004100000245016800041210006900209260008700278300001200365490000700377520194500384100001902329700001702348700002802365700002602393700002102419700001502440856013702455       2010                        eng d00aLinking DNA sequences to morphology: cryptic diversity and population genetic structure in the marine nematode Thoracostoma trachygaster (Nematoda, Leptosomatidae)0 aLinking DNA sequences to morphology cryptic diversity and popula  aCOMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USAbWILEY-BLACKWELL PUBLISHING, INC  a276-2890 v393 aRecent taxonomic and population genetic studies have revealed the presence of substantial cryptic diversity through sequence analysis of nematode morphospecies classified in different major clades. Correct interpretations of intra- and interspecific genetic variation require certainty about the conspecificity of the sequenced specimens, which in turn must depend on appropriate protocols with built-in verifiability procedures. In this study, we performed a population genetic study in the free-living marine nematode Thoracostoma trachygaster, a member of one of the earliest major clades to diverge in nematode phylogeny. We collected 367 nematodes from 11 populations located in the Californian Bight, all of which were video captured before DNA extraction to document and verify their individual morphology. Sequences for the cytochrome c oxidase subunit 1 (COI), D2D3 and 18S genes showed eight deeply divergent clades, and using a reverse taxonomy approach, six of these clades proved to be other morphospecies than T. trachygaster. Phylogenetic analyses of COI, internal transcribed spacer and D2D3 showed evidence for two sympatrically distributed cryptic species within the morphospecies T. trachygaster. Population genetic analyses of the most widespread cryptic species showed a moderate genetic structuring (Theta(ST) = 0.28), and 18% of this genetic variation was caused by differences between populations north and south of Point Conception. Within the southern Californian Bight, some genetic differentiation could be attributed to differences between populations north and south of Malibu, supporting the idea of a barrier to gene flow near Los Angeles region. The results for T. trachygaster support the contention that species diversity within free-living nematodes is underestimated, and that dispersal of marine nematodes from tidal environments associated with kelp holdfasts is substantial at scales of a few 100 km.1 aDerycke, Sofie1 aDe Ley, Paul1 aDe Ley, Irma, Tandingan1 aHolovachov, Oleksandr1 aRigaux, Annelien1 aMoens, Tom  uhttps://nematoda.myspecies.info/content/linking-dna-sequences-morphology-cryptic-diversity-and-population-genetic-structure-marine-n03474nas a2200469   4500008004100000245008900041210006900130260009000199300001200289490000700301520201200308653001602320653002302336653001602359653001202375653001402387653002602401653002102427653001302448653001402461653003202475653001502507653001602522653001302538653001602551653001302567100002602580700002502606700001702631700002802648700002902676700002602705700001402731700002102745700001502766700002002781700002402801700002202825700002102847700002502868856011102893       2007                        eng d00aAn improved molecular phylogeny of the Nematoda with special emphasis on marine taxa0 aimproved molecular phylogeny of the Nematoda with special emphas  a525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USAbACADEMIC PRESS INC ELSEVIER SCIENCE  a622-6360 v423 aPhylogenetic reconstructions of relations within the phylum Nematoda are inherently difficult but have been advanced with the introduction of large-scale molecular-based techniques. However, the most recent revisions were heavily biased towards terrestrial and parasitic species and greater representation of clades containing marine species (e.g. Araeolaimida, Chromadorida, Desmodorida, Desmoscolecida, Enoplida, and Monhysterida) is needed for accurate coverage of known taxonomic diversity. We now add small subunit ribosomal DNA (SSU rDNA) sequences for 100 previously un-sequenced species of nematodes, including 46 marine taxa. SSU rDNA sequences for > 200 taxa have been analysed based on Bayesian inference and LogDet-transformed distances. The resulting phylogenies provide support for (i) the re-classification of the Secernentea as the order Rhabditida that derived from a common ancestor of chromadorean orders Araeolaimida, Chromadorida, Desmodorida, Desmoscolecida, and Monhysterida and (ii) the position of Bunonema close to the Diplogasteroidea in the Rhabditina. Other, previously controversial relationships can now be resolved more clearly: (a) Alaimus, Campydora, and Trischistoma belong in the Enoplida, (b) Isolaimium is placed basally to a big clade containing the Axonolaimidae, Plectidae, and Rhabditida, (c) Xyzzors belongs in the Desmodoridae, (d) Comesomatidae and Cyartonema belongs in the Monhysterida, (e) Globodera belongs in the Hoplolaimidae and (0 Paratylenchus dianeae belongs in the Criconematoidea. However, the SSU gene did not provide significant support for the class Chromadoria or clear evidence for the relationship between the three classes, Enoplia, Dorylaimia, and Chromadoria. Furthermore, across the whole phylum, the phylogenetically informative characters of the SSU gene are not informative in a parsimony analysis, highlighting the short-comings of the parsimony method for large-scale phylogenetic modelling. (c) 2006 Elsevier Inc. All rights reserved.10aAdenophorea10aBayesian inference10aChromadorea10aEnoplea10aevolution10aLogDet transformation10aMarine nematodes10aNematoda10aparsimony10aphylogenetic reconstruction10aRhabditida10aSecernentea10aSSU rDNA10asystematics10ataxonomy1 aMeldal, Birgit, H. M.1 aDebenham, Nicola, J.1 aDe Ley, Paul1 aDe Ley, Irma, Tandingan1 aVanfleteren, Jacques, R.1 aVierstraete, Andy, R.1 aBert, Wim1 aBorgonie, Gaetan1 aMoens, Tom1 aTyler, Paul, A.1 aAusten, Melanie, C.1 aBlaxter, Mark, L.1 aRogers, Alex, D.1 aLambshead, P., J. D.  uhttps://nematoda.myspecies.info/content/improved-molecular-phylogeny-nematoda-special-emphasis-marine-taxa