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Morphological and molecular taxonomy of aquatic and terrestrial protists as a prerequisite for studies of evolution, biodiversity, biogeography, bioindication and ecosystem functioning –examples from euglyphid and arcellinid testate amoebae
Auteur(s)
Editeur(s)
Maison d'édition
Neuchâtel : Université de Neuchâtel
Date de parution
2023
Nombre de page
222
Résumé
Macro-eukaryotes (i.e., organisms that do not need magnification to be seen) appear to being the dominant component of ecosystems, but they are not the only driving forces of ecological processes. Microorganisms are known to play important roles in ecological processes such as elements, and nutrients cycling and are also known to shape macro-eukaryotic communities via parasitism or symbiosis (e.g., mycorrhiza). Now we are starting to assess the diversity and the impact on ecological processes of freshwater and marine micro-organisms but little is known of the soil-dwelling microbes, especially non-fungal and non-plant unicellular microeukaryotes (known as the protists). Maybe because most do not form recognizable colonies like the bacteria and the fungi, soil protists have been overlooked even by microbiologists. Some protists such as the diatoms, radiolarians, foraminiferans and coccolithophores have proved to be potent proxies and are commonly used to evaluate current or past environmental changes, but it concerns only a fraction of the protistan diversity. Furthermore, those are mostly marine organisms. Among the plethora of soil protists and their possible uses, only testate amoebae are regularly used as proxies to monitor the evolution of peatlands. And probably, one of the major reasons that could be invoked is the largely incomplete taxonomy of soil protists. The use of protists as bioindicators implies a sound taxonomic framework. However, the diversity and the taxonomy of these organisms is still far from being understood, as most species have not been described. Protists were mainly characterized with light microscopy, but the absence of characteristic morphological traits - and the fact that the phenotypical plasticity of protists was considered as being extremely high - has led naturalists to underestimate their diversity for a long time. It is only recently with the appearance of staining protocols, electron microscopy and molecular biology that we start to assess the true diversity of these organisms. With these new tools, it appears that many described species were in fact morphospecies complexes including more than one biological species that, sometimes, could be completely unrelated. Among these tools, High Throughput Sequencing (HTS) allows to evaluate more easily the micro-eukaryotic community of an environmental sample, revealing that many clades of protists have not been characterized and are still to be discovered. There is then a need for taxonomists to describe this hidden diversity and to update old descriptions in order to build a sound taxonomy. The aim of this thesis is to cover the several steps required to improve the taxonomy of soil protists, with a focus on testate amoebae, so that they can be used in larger surveys to study their ecology, diversity and evolution.
Notes
PhD thesis to obtain the title of Doctor of Philosophy in Biological Science of the University of Neuchâtel
Direction: Prof. Edward Mitchell
Members or the jury
Prof. Alastair Simpson, Dalhousie University, Canada
Dr Guillaume Lentendu, Université de Neuchâtel, Suisse
Dr Christophe Praz, Université de Neuchâtel, Suisse
Dr Enrique Lara, Real Jardín Botánico, CSIC, Madrid
Prof. tit. Nadir Alvarez, Université de Genève, Suisse
Defended the 30th of September 2022
Direction: Prof. Edward Mitchell
Members or the jury
Prof. Alastair Simpson, Dalhousie University, Canada
Dr Guillaume Lentendu, Université de Neuchâtel, Suisse
Dr Christophe Praz, Université de Neuchâtel, Suisse
Dr Enrique Lara, Real Jardín Botánico, CSIC, Madrid
Prof. tit. Nadir Alvarez, Université de Genève, Suisse
Defended the 30th of September 2022
Identifiants
Type de publication
doctoral thesis
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