Raissalyn Kneisel (Justus-Liebig-Universität Gießen)
Raissalyn Monika Estela Kneisel's Master thesis was awarded with the Prize for the Best Plant Science Master Thesis, which was carried out at Giessen University in the year 2025 with the title:
Population genetic analysis of Cotoneaster bullatus and Cotoneaster divaricatus (Rosaceae), two non-native, potentially invasive woody species in Central Hesse
The ISSR-based population genetic analysis of the naturalized species Cotoneaster bullatus and Cotoneaster divaricatus (Rosaceae) – primarily from distribution areas in Central Hesse – aimed to assess their genetic diversity and differentiation as well as to evaluate their potential invasiveness, whereas C. divaricatus is characterized by genetic homogeneity and high intra-specific variability, making it particularly adaptable and thus potentially invasive, whilst C. bullatus shows greater genetic differentiation between populations.
The species-rich family Rosaceae (the rose family) represents one of the most economically significant plant groups in horticulture. This includes the genus Cotoneaster, whose representatives are widely distributed across urban green spaces and ornamental plantings. Accordingly, the focus of this population genetic analysis was placed on the species C. bullatus and C. divaricatus, whose tendencies toward naturalization make them a potentially relevant subject for applied conservation research.
The study comprised 100 individuals, primarily consisting of feral plants of C. bullatus and C. divaricatus collected from seven sites in Central Hesse, along with a natural outgroup from the island of Amrum. In addition, leaf material from 16 further Cotoneaster species, cultivated at the Botanical Garden of Jena, was included as a cultivar outgroup. Following successful DNA extraction, both molecular and statistical analyses were conducted. The two main analytical approaches involved assessing genetic correlations among samples and evaluating population genetic parameters, such as genetic diversity and its distribution.
The application of various statistical tests revealed high intraspecific genetic diversity but moderate to low genetic differentiation among populations of the focal species C. bullatus and C. divaricatus from Central Hesse. Furthermore, the results indicated that within the genus Cotoneaster an ongoing evolutionary process appears to be taking place, shaped by the interplay of genetic variability, hybridization, and apomixis – a form of asexual reproduction. The high invasiveness potential of C. divaricatus is further supported by its genetic homogeneity combined with high intraspecific variability, whereas C. bullatus shows greater genetic differentiation among populations. These findings allow potential implications and suitable management strategies to be drawn regarding the spread of Cotoneaster species into conservation-relevant habitats.
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Raissalyn M. E. Kneisel conducted this work at the chair of Special Botany (Spezielle Botanik) at the Justus-Liebig-University Giessen in the working group of Prof. Dr. Volker Wissemann.