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Josephine Franke (Universität Rostock)

Josephine Franke's Master thesis was awarded with the Prize for the Best Plant Science Master Thesis, which was carried out at Universität Rostock in the year 2022

Title: Taxonomic analyses of clonal cultures belonging to the genus Pantocsekiella based on sequence analyses of various genetic markers

The thesis made a significant contribution to the taxonomy of an important diatom genus by using a variety barcoding markers, some of which have not been used previously. The chosen Pantocsekiella is an important bioindicator for water quality assessments, but its morphology made this challenging due to its highly variable morphology. 

Diatoms are excellent bioindicators of current or past conditions of a water body. Species identification is done using morphological characteristics of the detailed cell walls and can be complemented by molecular methods. In this work, in addition to some barcoding markers already established for diatoms, further DNA regions were tested for their suitability within the genus under consideration. Using these molecular data, an attempt was made to resolve ambiguities within the genus Pantocsekiella K.T. KISS & ÁCS. It contains several species with variable characters, which may make identification difficult. The sequences of clonal cultures for five DNA regions (chloroplastid, mitochondrial, and nuclear) were amplified using PCR and then sequenced. The sequences thus obtained were evaluated with the result that some taxa were not molecularly distinct (P. ocellata (PANTOCSEK) K.T. KISS & E. ÁCS, P. kuetzingiana (THWAITES) K.T. KISS & E. ÁCS, and P. polymorpha (B. MEYER & HAKANSSON) K.T. KISS & E. ÁCS). Others showed molecular variability but could not be clearly separated into groups corresponding to taxa previously assigned based on morphological characters (P. comensis (GRUNOW) K.T. KISS & E. ÁCS, P. pseudocomensis (SCHEFFLER) K.T. KISS & E. ÁCS, P. costei (DRUART & STRAUB) K.T. KISS & E. ÁCS, P. delicatula (HUSTEDT) K.T. KISS & E. ÁCS, P. hinziae (HOUK, KÖNIG & KLEE) K.T. KISS & E. ÁCS). Whether it is one species with intraspecific morphological as well as molecular variability or several species, which do not correspond to the previous classifications cannot be clarified unambiguously and conclusively on the basis of the data obtained here. This can be the starting point for further investigations. The newly considered barcoding markers could be easily applied to the genus and should be tested in further taxa. Separation and correct description of diatom species is relevant in that even very similar species can show different tolerances and responses to environmental parameters, increasing the potential for meaningful application as bioindicators.


Josephine Franke conducted this work at the Institute / Chair of General and Special Botany in the working group of Dr. Thomas Hübener.