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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

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  • Publication
    Métadonnées seulement
    The testate lobose amoebae (order Arcellinida Kent, 1880) finally find their home within Amoebozoa
    (2005)
    Nikolaev, Sergey I
    ;
    Mitchell, Edward 
    ;
    Petrov, Nikolay B
    ;
    Berney, Cédric
    ;
    Fahrni, José
    ;
    Pawlowski, Jan
    Testate lobose amoebae (order Arcellinida Kent, 1880) are common in all aquatic and terrestrial habitats, yet they are one of the last higher taxa of unicellular eukaryotes that has not found its place in the tree of life. The morphological approach did not allow to ascertain the evolutionary origin of the group or to prove its monophyly. To solve these challenging problems, we analyzed partial small-subunit ribosomal RNA (SSU rRNA) genes of seven testate lobose amoebae from two out of the three suborders and seven out of the 13 families belonging to the Arcellinida. Our data support the monophyly of the order and clearly establish its position among Amoebozoa, as a sister-group to the clade comprising families Amoebidae and Hartmannellidae. Complete SSU rRNA gene sequences from two species and a partial actin sequence from one species confirm this position. Our phylogenetic analyses including representatives of all sequenced lineages of lobose amoebae suggest that a rigid test appeared only once during the evolution of the Amoebozoa, and allow reinterpretation of some morphological characters used in the systematics of Arcellinida. (c) 2005 Published by Elsevier GmbH.
  • Publication
    Métadonnées seulement
    Vertical micro-distribution and response to nitrogen deposition of testate amoebae in Sphagnum
    (2004)
    Mitchell, Edward 
    ;
    Gilbert, Daniel
    Previous studies have shown the existence of a vertical micro-distribution of testate amoebae in the first centimeters of Sphagnum and their response to nutrient enrichment. In order to test the response of testate amoebae to depth and N addition in dry moss carpets recolonizing cutover peatlands, we sampled Sphagnum that had received 0, 1, 3, or log N M-2 yr(-1) for three years. The mosses were cut into three segments: 0-1 cm, 1-3 cm and 3-5 cm and analyzed for testate amoebae. The overall diversity (22 taxa) was high considering the dryness of the site, but the species richness of individual samples was low (mean 6.6). The presence of several species characteristic of wetter conditions suggests that they have a broader tolerance than usually believed and/or have a high colonization potential. Species richness increased with depth. Assulina muscorum was most abundant in the top segment, while Phryganella acropodia, Heleopera rosea and Nebela militaris were most abundant in the deepest segment. Neither the metabolism type nor the shell characteristics significantly explained the vertical distribution of species. There was no overall response of testate amoebae to N, although one species, Bullinularia indica, was significantly more abundant in the fertilized than in the control plots.