Fiche participant :
Nom : Cohen
Prénom : Bernard
Liste des participations aux campagnes accessibles
- NORFOLK 1
- Collecte - Tri (Systématique moléculaire, University of Glasgow)
Bibliographie (7) [+] [-]
Exporter les bibliographies
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Bitner M.A., Cohen B.L., Long S.L., Richer de forges B. & Saito M.A. 2007. Gyrothyris williamsi sp. nov. and inter-relationships of some taxa from waters around New Zealand and the southern oceans (Rhynchonelliformea: Terebratelloidea). Earth and Environmental Science Transactions of the Royal Society of Edinburgh 98(3-4). DOI:10.1017/S1755691008075142
Résumé [+] [-]This paper describes a terebratelloid articulate brachiopod, Gyrothyris williamsi sp. nov., based on 95 specimens from seamounts on the Lord Howe Rise, Coral Sea, SW Pacific Ocean. The new species is attributed to Gyrothyris on the basis of (a) morphological and growth trajectory similarities; (b) phylogenetic analyses of an alignment of DNA sequence (similar to 2900-sites) obtained from nuclear-encoded small- and large-subunit ribosomal RNA genes (SSU and LSO; and (c) the presence of a distinctive, two-part deletion in the LSU gene. It is distinguished morphologically from Gyrothyris mawsoni and its subspecies by both internal and external morphology and by its isolated geographical distribution, which extends the patchy, known range of this genus to an area some 2000 km north of its previous northern limit around New Zealand. Phylogenetic analyses of the rDNAs and of mitochondrial cox1 gene sequences (663 sites) confirm previous indications that the New Zealand endemic terebratelloid genera form a clade (Neothyris (Calloria, Gyrothyris, Terebratella), but the position of Terebratella with respect to Calloria and Gyrothyris remains weakly established. These sequences disagree inexplicably about the closeness of the relationship between Neothyris parva and N. lenticidaris. Analyses of the first sequences from Calloria variegata, a species restricted to the Hauraki Gulf, New Zealand, are consistent with the possibility that it originated locally, and recently, from C inconspicua. Magellania venosa from S. America/Falklands joins with Antarctic Magellaninia fragilis and M. joubini to form an rDNA clade that excludes Terebratalia as the putative sister-group of the New Zealand terebratelloid clade. The cox1(but not the rDNA) sequences of the New Zealand clade pass a test for clock-like rates of evolution, and maximum likelihood pairwise distances suggest that if genetic isolation between the ancestor of Antarctic Magellania and the last common ancestor of the New Zealand terebratelloid clade was initiated by separation of the Antarctic and New Zealand plates similar to 90 Mya, isolation from M. venosa was initiated earlier, perhaps similar to 145 Mya. However, in the simple phylogenctic reconstruction presented here from cox1 sequences, S. American and Antarctic Magellania spp. do not yield a well-supported clade, perhaps because of differences in base composition.
Campagnes accessibles citées (1) [+] [-]
Codes des collections associés: IB (Bryozoaires Brachiopodes) -
Bitner M.A. & Cohen B.L. 2015. Congruence and conflict: case studies of morphotaxonomy versus rDNA gene tree phylogeny among articulate brachiopods (Brachiopoda: Rhynchonelliformea), with description of a new genus. Zoological Journal of the Linnean Society 173(2): 486-504. DOI:10.1111/zoj.12217
Campagnes accessibles citées (1) [+] [-]
Codes des collections associés: IB (Bryozoaires Brachiopodes) -
Cohen B.L., Stark S., Gawthrop A., Burke M.E. & Thayer C.W. 1998. Comparison of articulate brachiopod nuclear and mitochondrial gene trees leads to a clade-based redefinition of protostomes (Protostomozoaand ) and deuterostomes (Deuterostomozoa). Proceedings of the Royal Society B: Biological Sciences 265: 475-482
Résumé [+] [-]Nuclear and mtDNA sequences from selected short-looped terebratuloid (terebratulacean) articulate brachiopods yield congruent and genetically independent phylogenetic reconstructions by parsimony, neighbour-joining and maximum likelihood methods, suggesting that both sources of data are reliable guides to brachiopod species phylogeny. The present-day genealogical relationships and geographical distributions of the tested terebratuloid brachiopods are consistent with a tethyan dispersal and subsequent radiation. Concordance of nuclear and mitochondrial gene phylogenies reinforces previous indications that articulate brachiopods, inarticulate brachiopods, phoronids and ectoprocts cluster with other organisms generally regarded as protostomes. Since ontogeny and morphology in brachiopods, ectoprocts and phoronids depart in important respects from those features supposedly diagnostic of protostomes, this demonstrates that the operational definition of protostomy by the usual ontological characters must be misleading or unreliable. New, molecular, operational definitions are proposed to replace the traditional criteria for the recognition of protostomes and deuterostomes, and the clade-based terms 'Protostomozoa' and 'Deuterostomozoa' are proposed to replace the existing terms 'Protostomia' and 'Deuterostomia'.
Campagnes accessibles citées (4) [+] [-]
Codes des collections associés: IB (Bryozoaires Brachiopodes) -
Cohen B.L., Gawthrop A. & Cavalier-smith T. 1998. Molecular phylogeny of Brachiopods and Phoronids based on nuclear-encoded small subunit ribosomal RNA gene sequences. Philosophical Transactions of the Royal Society 353: 2039-2061
Résumé [+] [-]Brachiopod and phoronid phylogeny is inferred from SSU rDNA sequences of 28 articulate and nine in- articulate brachiopods, three phoronids, two ectoprocts and various outgroups, using gene trees reconstructed by weighted parsimony, distance and maximum likelihood methods. Of these sequences, 33 from brachiopods, two from phoronids and one each from an ectoproct and a priapulan are newly determined. The brachiopod sequences belong to 31 di¡erent genera and thus survey about 10% of extant genus-level diversity. Sequences determined in di¡erent laboratories and those from closely related taxa agree well, but evidence is presented suggesting that one published phoronid sequence (GenBank acces- sion U12648) is a brachiopod phoronid chimaera, and this sequence is excluded from the analyses. The chiton, Acanthopleura, is identi¢ed as the phenetically proximal outgroup; other selected outgroups were chosen to allow comparison with recent, non-molecular analyses of brachiopod phylogeny. The di¡erent outgroups and methods of phylogenetic reconstruction lead to similar results, with di¡erences mainly in the resolution of weakly supported ancient and recent nodes, including the divergence of inarticulate brachiopod sub-phyla, the position of the rhynchonellids in relation to long- and short-looped articulate brachiopod clades and the relationships of some articulate brachiopod genera and species. Attention is drawn to the problem presented by nodes that are strongly supported by non-molecular evidence but receive only low bootstrap resampling support.
Campagnes accessibles citées (1) [+] [-]
Codes des collections associés: IB (Bryozoaires Brachiopodes) -
Cohen B.L., Améziane N., Eleaume M. & Richer de forges B. 2004. Crinoid phylogeny: a preliminary analysis (Echinodermata: Crinoidea). Marine Biology 144(3): 605-617. DOI:10.1007/s00227-003-1212-7
Résumé [+] [-]We describe the first molecular and morphological analysis of extant crinoid high-level inter-relationships. Nuclear and mitochondrial gene sequences and a cladistically coded matrix of 30 morphological characters are presented, and analysed by phylogenetic methods. The molecular data were compiled from concatenated nuclear-encoded 18S rDNA, internal transcribed spacer 1, 5.8S rDNA, and internal transcribed spacer 2, together with part of mitochondrial 16S rDNA, and comprised 3,593 sites, of which 313 were parsimony-informative. The molecular and morphological analyses include data from the bourgueticrinid Bathycrinus; the antedonid comatulids Dorometra and Florometra; the cyrtocrinids Cyathidium, Gymnocrinus, and Holopus; the isocrinids Endoxocrinus, and two species of Metacrinus; as well as from Guillecrinus and Caledonicrinus, whose ordinal relationships are uncertain, together with morphological data from Proisocrinus. Because the molecular data include indel-rich regions, special attention was given to alignment procedure, and it was found that relatively low, gene-specific, gap penalties gave alignments from which congruent phylogenetic information was obtained from both well-aligned, indel-poor and potentially misaligned, indel-rich regions. The different sequence data partitions also gave essentially congruent results. The overall direction of evolution in the gene trees remains uncertain: an asteroid outgroup places the root on the branch adjacent to the slowly evolving isocrinids (consistent with palaeontological order of first appearances), but maximum likelihood analysis with a molecular clock places it elsewhere. Despite lineage-specific rate differences, the clock model was not excluded by a likelihood ratio test. Morphological analyses were unrooted. All analyses identified three clades, two of them generally well-supported. One well-supported clade (BCG) unites Bathycrinus and Guillecrinus with the representative (chimaeric) comatulid in a derived position, suggesting that comatulids originated from a sessile, stalked ancestor. In this connection it is noted that because the comatulid centrodorsal ossicle originates ontogenetically from the column, it is not strictly correct to describe comatulids as "unstalked" crinoids. A second, uniformly well-supported clade contains members of the Isocrinida, while the third clade contains Gymnocrinus, a well-established member of the Cyrtocrinida, together with the problematic taxon Caledonicrinus, currently classified as a bourgueticrinid. Another cyrtocrinid, Holopus, joins this clade with only weak molecular, but strong morphological support. In one morphological analysis Proisocrinus is weakly attached to the isocrinid clade. Only an unusual, divergent 18S rDNA sequence was obtained from the morphologically strange cyrtocrinid Cyathidium. Although not analysed in detail, features of this sequence suggested that it may be a PCR artefact, so that the apparently basal position of this taxon requires confirmation. If not an artefact, Cyathidium either diverged from the crinoid stem much earlier than has been recognised hitherto (i.e., it may be a Palaeozoic relic), or it has an atypically high rate of molecular evolution.
Campagnes accessibles citées (5) [+] [-]
Codes des collections associés: IE (Échinodermes) -
Cohen B.L. & Pisera A. 2016. Crinoid phylogeny: new interpretation of the main Permo-Triassic divergence, comparisons with echinoids and brachiopods, and EvoDevo interpretations of major morphological variations. Biological Journal of the Linnean Society. DOI:10.1111/bij.12868
Campagnes accessibles citées (1) [+] [-]
Codes des collections associés: IE (Échinodermes) -
Cohen B.L. & Pisera A. 2017. Crinoid phylogeny: new interpretation of the main Permo-Triassic divergence, comparisons with echinoids and brachiopods, and EvoDevo interpretations of major morphological variations. Biological Journal of the Linnean Society 120: 38-53. DOI:10.1111/bij.12868
Campagnes accessibles citées (2) [+] [-]
Codes des collections associés: IB (Bryozoaires Brachiopodes)