Vignette d'image

Mitchell, Edward

Nom
Mitchell, Edward
Affiliation principale
Site web
Fonction
Professeur ordinaire
Email
edward.mitchell@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/357
_
0000-0003-0358-506X

Résultat de la recherche

Filtres

2
2
2
Réinitialiser les filtres

Paramètres

Voici les éléments 1 - 2 sur 2
  • Publication
    Accès libre
    COI Barcoding of Nebelid Testate Amoebae (Amoebozoa: Arcellinida): Extensive Cryptic Diversity and Redefinition of the Hyalospheniidae Schultze
    (2012)
    Kosakyan, Anush 
    ;
    Heger, Thierry J.
    ;
    Leander, Brian S.
    ;
    Todorov, Milcho
    ;
    Mitchell, Edward 
    ;
    Lara, Enrique 
    We used Cytochrome Oxidase Subunit 1 (COI) to assess the phylogenetic relationships and taxonomy of Nebela sensu stricto and similar taxa (Nebela group, Arcellinida) in order to clarify the taxonomic validity of morphological characters. The COI data not only successfully separated all studied morphospecies but also revealed the existence of several potential cryptic species. The taxonomic implications of the results are: (1) Genus Nebela is paraphyletic and will need to be split into at least two monophyletic assemblages when taxon sampling is further expanded. (2) Genus Quadrulella, one of the few arcellinid genera building its shell from self-secreted siliceous elements, and the mixotrophic Hyalosphenia papilio branch within the Nebela group in agreement with the general morphology of their shell and the presence of an organic rim around the aperture (synapomorphy for Hyalospheniidae). We thus synonymise Hyalospheniidae and Nebelidae. Hyalospheniidae takes precedence and now includes Hyalosphenia, Quadrulella (previously in the Lesquereusiidae) and all Nebelidae with the exception of Argynnia and Physochila. Leptochlamys is Arcellinida incertae sedis. We describe a new genus Padaungiella Lara et Todorov and a new species Nebela meisterfeldi n. sp. Heger et Mitchell and revise the taxonomic position (and rank) of several taxa. These results show that the traditional morphology-based taxonomy underestimates the diversity within the Nebela group, and that phylogenetic relationships are best inferred from shell shape rather than from the material used to build the shell.
  • Publication
    Accès libre
    Comparing Potential COI and SSU rDNA Barcodes for Assessing the Diversity and Phylogenetic Relationships of Cyphoderiid Testate Amoebae (Rhizaria: Euglyphida)
    (2011)
    Heger, Thierry J.
    ;
    Pawlowski, Jan
    ;
    Lara, Enrique 
    ;
    Leander, Brian S.
    ;
    Todorov, Milcho
    ;
    Golemansky, Vassil
    ;
    Mitchell, Edward 
    The mitochondrial Cytochrome Oxidase Subunit 1 gene (COI) has been promoted as an ideal “DNA barcode” for animal species and other groups of eukaryotes. However, the utility of the COI marker for species level discrimination and for phylogenetic analyses has yet to be tested within the Rhizaria. Accordingly, we analysed mitochondrial COI gene sequences and nuclear small subunit rDNA (SSU) sequences from several morphospecies of euglyphid testate amoebae (Cercozoa, Rhizaria) in order to evaluate the utility of these DNA markers for species discrimination and phylogenetic reconstructions. Sequences were obtained from eleven populations belonging to six Cyphoderia morphospecies that were isolated from field samples in North America and Europe. Mean inter-population COI sequence dissimilarities were on average 2.9 times greater than in the SSU, while the intra-population sequence dissimilarities were higher in the SSU (0-0.95%) than in the COI (0%); this suggests that the COI fragment is valuable for discriminating Cyphoderiidae isolates. Our study also demonstrated that COI sequences are useful for inferring phylogenetic relationships among Cyphoderiidae isolates. COI and SSU tree topologies were very similar even though the COI fragment used in these analyses (500 bp) was much shorter than the SSU sequences (1600 bp). Altogether, these results demonstrate the utility of the COI as a potential taxonomic DNA barcode for assessing cyphoderiid species diversity and for inferring phylogenetic relationships within the group.