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Title: Diversity of silica-scaled protists
Author: Scoble, Josephine Margaret
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2013
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This thesis investigates the diversity of two silica-scaled protist groups, Paraphysomonadida and Thaumatomonadida by light and electron microscopical observations and sequencing (rDNA) on novel clonal cultures. Despite these groups of protist dominating pelagic, littoral as well as inland freshwater and soil habitats, they are taxonomically poorly understood to the extent that any progress in ecological theory is hampered. Now that environmental DNA sequencing is being carried out faster than we can characterise protists from culture it is important that we understand how molecular and physical diversity match up, especially because so many protists are morphospecies. Nearly one hundred isolates were cultured on which both morphological and molecular data was carried out in parallel to reveal around 50 new species of protist from eight different genera: two heterokont genera, Paraphysomonas and Incisomonas n. gen., and six cercozoan genera, Thaumatomonas, Allas, Reckertia, Thaumatospina n. gen., Cowlomonas n. gen., and Scutellomonas n. gen. These data make major contributions to taxonomy and understanding aspects of protist diversity where previously morphological diversity was heavily biased towards over- generalized morphotypes. This thesis quickly showed that gross lumping of morphospecies was true of Paraphysomonas, for which many of the isolates cultured herein might have been regarded as one species (not more than 20). The many cultured isolates exhibited varied cell and scale morphology, and by sequencing (rDNA), it was possible to see the evolution of scale morphology map on to trees. This marriage of molecular and morphological data made it possible to view distinct groups of species that shared scale detail that might have otherwise been overlooked had either method been used alone. This research has shed significant light on how scale morphology can be used as reliable taxonomic marker for protists, the insights of which can be applied to make taxonomic improvements to other silica-scaled protist groups.
Supervisor: Cavalier-Smith, T. Sponsor: Biotechnology and Biological Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Science ; Zoology ; Microbiology ; Protistology ; Phycology ; microscopy ; protists ; biology ; taxonomy ; algae ; phylogeny ; ribosome ; secondary structure ; ultrastructure ; electron microscopy ; light microscopy