Assessing phylogenetic delineations of taxa of filamentous Xanthophyceae (Stramenopiles) using DNA sequence analyses and morphology

• Main Author: Rybalka, Nataliya
• Other Authors: Schulz, Rüdiger, Ober, Dietrich
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2015
• Subjects: thesis; ddc:580; Xanthophyceae; Stramenopiles; algae; Taxonomy; phylogenetic analyses of DNA; Algen; Taxonomie; phylogenetische Analysen von DNA-Sequenzen; Antarctic; Antarc*
• Online Access: https://nbn-resolving.org/urn:nbn:de:gbv:8-diss-185215; https://macau.uni-kiel.de/receive/diss_mods_00018521; https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/dissertation_derivate_00006515/Rybalka_PhD_thesis_final_150812publ.pdf

This thesis focuses on assessing taxonomic boundaries among the filamentous members of “yellow-green algae”, i.e. the class Xanthophyceae (Stramenopiles), which are widespread microalgae in freshwater or terrestrial habitats. The scarcity of morphological characters as well as their considerable plasticity requires the employment of molecular marker sequences to define monophyletic genera and species as well as for the unambiguous identification of new isolates. The genetic diversity and species boundaries within genera of Tribonemataceae, i.e Xanthonema Silva, Bumilleria Borzì, Bumilleriopsis Printz, Pseudobumilleriopsis Deason & Bold and Tribonema Derbès & Solier, were assessed using the highly variable psbA/rbcL spacer region as well as the more conserved full rbcL gene sequences. A method and a reference data base for the unambiguous identification of species of Heterococcus Chodat which uses DNA sequence variation in markers from plastid and nuclear genomes were established. In all studied cases the molecular-based species boundaries were more conservative than those defined by morphology. Within a single species almost identical genotypes were repeatedly recovered from strains of different geographic origins. However, the genotypes recovered from Antarctic strains were distinct from those of temperate regions. Die vorliegende Arbeit hat zum Ziel taxonomische Abgrenzungen bei fadenförmigen „Gelbgrünalgen“, d.h. Vertretern der Klasse Xanthophyceae (Stramenopiles), festzustellen. Fadenförmige Xanthophyceae sind weitverbreitete Mikroalgen im Süßwasser und in terrestrischen Lebensräumen. Da diese Algen arm an morphologischen Merkmalen sind und diese zudem eine beträchtliche Plastizität aufweisen, ist es notwendig, molekulare Markersequenzen einzusetzen, um monophyletische Gattungen und Arten zu definieren und neue Isolate auf Artniveau eindeutig bestimmen zu können. Die genetische Diversität und die Abgrenzungen von Gattungen der Tribonemataceae, d.h. Xanthonema Silva, Bumilleria Borzì, Bumilleriopsis ...