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Polyphasic approach to the study of diatom diversity
Kollár, J. (2020). Polyphasic approach to the study of diatom diversity. PhD Thesis. Palacký University Olomouc, Faculty of Science, Department of Botany: Olomouc. [Diff. pag.] pp.
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| Beschikbaar in | Auteur |
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Documenttype: Doctoraat/Thesis/Eindwerk
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| Trefwoorden |
Classification > Taxonomy
Geography > Biogeography
Pinnularia C.G. Ehrenberg, 1843 [WoRMS]
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| Author keywords |
cryptic species diversity, LSU rDNA, morphology, polyphasic systematics, rbcL, species, SSU rDNA |
| Abstract |
Diatoms are one of the most species-rich groups of algae. As a group, they are cosmopolitan and adapted to almost all aquatic and some terrestrial habitats. Consequently, they are of great significance not only to fundamental research in the fields of biodiversity, evolutionary biology, ecology, and paleolimnology, but also for applied disciplines such as biomonitoring, biotechnology, and nanotechnology. For many of them, it is key to use correct taxonomic identifications which reflect an evolutionary history of the lineages in question. In this regard, one of the most serious challenges faced by contemporary diatomologists is the problem of cryptic and pseudocryptic species diversity. In the light shed by new technologies and approaches, many traditionally described diatom species appeared to be (pseudo)cryptic species complexes rather than single species. Several presumed species complexes are included in the genus Pinnularia, the P. gibba group among them. In this dissertation, I have gathered a data set of 105 P. gibba group strains with worldwide origin and used it to delimit species by means of a polyphasic approach. The primary (i.e., DNA-based) species delimitation based on two genetic markers and three automatized species delimitation methods revealed that the data set covered 15 species of the group. The secondary species delimitation rested in confrontation of this primary hypothesis with other available lines of evidence, namely with morphological, geographic, environmental and/or reproductive data. I conclude that the data set indeed covered 15 species many of which are (pseudo)cryptic with limited geographic distributions. An addition of more conserved genetic marker along with the fossil data allowed for an inference of time-calibrated phylogeny. The phylogeny further allowed for formulation and (in same cases) statistical testing of some evolutionary and biogeographic hypotheses. For example, significant difference in cell-size was detected in different parts of the tree and the difference is currently best explained by an evolutionary origin. Concerning the identification of the delimited species, proposed diatom DNA barcode markers in rbcL and SSU rDNA can unambiguously distinguish even between (pseudo)cryptic sister species of the group. Furthermore, the taxonomic review of the group was initiated by formal description of one of the delimited species as P. lacustrigibba sp. nov. Finally, the dissertation led to a development of a novel probabilistic model of speciation which, perhaps, may form a theoretical basis for future development of a new kind of probabilistic species delimitation methods applicable even to incipient species (many of which are presumably cryptic) and most of the asexual lineages. |
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