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Université de Neuchâtel

Using testate amoeba community structure and functional diversity to assess the impact of climate changes on ecosystem functioning : finding relevant and convenient tools for bio-monitoring of "Sphagnum" peatlands evolution or recovery

Koenig, Isabelle ; Mitchell, Edward AD (Dir.) ; Le Bayon, Claire (Codir.)

Thèse de doctorat : Université de Neuchâtel, 2017.

Human activity and ongoing climate changes have an increasing impact on ecosystems and lead to the loss of several natural habitats. Ecosystems provide functions contributing to human well-being and these functions could be estimated based on a monetary value. Among these ecosystems, wetlands and peatlands are of primary importance, by hosting a specific flora and acting as a carbon sink. Their...

Université de Neuchâtel

Phylogeny, systematics and ecology of free living protists : case study: family Hyalospheniidae

Kosakyan, Anush ; Mitchell, Edward (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2014.

Despite the fact that free-living protists compose the major part of Earth’s eukaryotic biodiversity and play numerous essential roles in ecosystems, knowledge on their true diversity, evolution and ecology remain highly limited. In this thesis I choose testate amoebae as a model group to address several key questions on the diversity, evolution and ecology of free-living protists. Family...

Université de Neuchâtel

Above- and belowground linkages in Sphagnum peatland : climate warming affects plant-microbial interactions

Jassey, Vincent E. J. ; Chiapusio, Geneviève ; Binet, Philippe ; Buttler, Alexandre ; Laggoun-Défarge, Fatima ; Delarue, Frédéric ; Bernard, Nadine ; Mitchell, Edward A. D. ; Toussaint, Marie-Laure ; Francez, André-Jean ; Gilbert, Daniel

In: Global Change Biology, 2013, vol. 19, no. 3, p. 811-823

Peatlands contain approximately one third of all soil organic carbon (SOC). Warming can alter above- and belowground linkages that regulate soil organic carbon dynamics and C-balance in peatlands. Here we examine the multiyear impact of in situ experimental warming on the microbial food web, vegetation, and their feedbacks with soil chemistry. We provide evidence of both positive and...

Université de Neuchâtel

Testate Amoebae Examined by Confocal and Two-Photon Microscopy: Implications for Taxonomy and Ecophysiology

Burdíková, Zuzana ; Čapek, Martin ; Ostašov, Pavel ; Machač, Jiří ; Pelc, Radek ; Mitchell, Edward A. D. ; Kubínová, Lucie

In: Microscopy and Microanalysis, 2010, vol. 16, p. 735-746

Testate amoebae (TA) are a group of free-living protozoa, important in ecology and paleoecology. Testate amoebae taxonomy is mainly based on the morphological features of the shell, as examined by means of light microscopy or (environmental) scanning electron microscopy (SEM/ESEM). We explored the potential applications of confocal laser scanning microscopy (CLSM), two photon excitation...

Université de Neuchâtel

Rediscovery of Nebela ansata (Amoebozoa: Arcellinida) in eastern North America: biogeographical implications

Heger, Thierry J. ; Booth, Robert K. ; Sullivan, Maura E. ; Wilkinson, David M. ; Warner, Barry G. ; Asada, Taro ; Mazei, Yuri ; Meisterfeld, Ralf ; Mitchell, Edward A. D.

In: Journal of Biogeography, 2011, vol. 38, no. 10, p. 1897-1906

Aim The question whether free-living protists are generally cosmopolitan is currently a matter of debate. In this study we investigate the geographical distribution of a distinctive testate amoeba species, Nebela ansata, and use our data to assess the potential for highly restricted distribution patterns in some protist species. Location Global. ...

Université de Neuchâtel

COI gene and ecological data suggest size-dependent high dispersal and low intra-specific diversity in free-living terrestrial protists (Euglyphida: Assulina)

Lara, Enrique ; Heger, Thierry J. ; Scheihing, Rodrigo ; Mitchell, Edward A. D.

In: Journal of Biogeography, 2010, vol. 38, no. 4, p. 640-650

Aim Propagule size and ecological requirements are believed to be major factors influencing the passive dispersal of free-living terrestrial protists. We compared the colonization potential of three closely related testate amoeba species (Assulina muscorum, A. seminulum, A. scandinavica, ranging from 40 to 100 μm in length). Location Europe. Methods ...

Université de Neuchâtel

The perils of taxonomic inconsistency in quantitative palaeoecology: experiments with testate amoeba data

Payne, Richard J. ; Lamentowicz, Mariucz ; Mitchell, Edward A. D.

In: Boreas, 2011, vol. 40, no. 17, p. 15-27

A fundamental requirement of quantitative palaeoecology is consistent taxonomy between a modern training set and palaeoecological data. In this study we assess the possible consequences of violation of this requirement by simulating taxonomic errors in testate amoeba data. Combinations of easily confused taxa were selected, and data manipulated to reflect confusion of these taxa; transfer...

Université de Neuchâtel

Highly Diverse and Seasonally Dynamic Protist Community in a Pristine Peat Bog

Lara, Enrique ; Mitchell, Edward A. D. ; Moreira, David ; López-García, Purificación

In: Protist, 2011, vol. 162, no. 1, p. 14-32

Culture-independent molecular methods based on the amplification, cloning and sequencing of small-subunit ribosomal RNA genes (SSU rDNAs) are powerful tools to study the diversity of microorganisms. Despite so, the eukaryotic microbial diversity of many ecosystems, including peatlands has not yet received much attention. We analysed the eukaryotic diversity by molecular surveys in water from the...

Université de Neuchâtel

Comparing Potential COI and SSU rDNA Barcodes for Assessing the Diversity and Phylogenetic Relationships of Cyphoderiid Testate Amoebae (Rhizaria: Euglyphida)

Heger, Thierry J. ; Pawlowski, Jan ; Lara, Enrique ; Leander, Brian S. ; Todorov, Milcho ; Golemansky, Vassil ; Mitchell, Edward A. D.

In: Protist, 2011, vol. 162, no. 1, p. 131-141

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)...