Polyploidisation plays a major role in plant evolution. It can also cause taxonomic complexities as morphological differences are often blurred in higher ploidy levels. One of the taxonomically-intrigued groups of Central Europe is C. rotundifolia agg. Three ploidy- heterogeneous species are traditionally recognized in the Czech Republic: C. gentilis (2x, 4x), C. rotundifolia (2x, 4x) and C. moravica (4x, 6x). The thesis examines karyological and phenotypic variation of C. moravica, in the centre of its distribution (the Czech Republic and Slovakia). With the aid of modern biosystematics tools (DNA flow cytometry, multivariate morphometrics), marked discrepancies were revealed between published data and actual cytotype distribution pattern and morphological variation. In contrast to literature records, cytotype distribution in C. moravica is largely parapatric, with hexaploids occurring in Pannonian basin and tetraploids in Central and Eastern Slovakia. The type population of presumed tetraploids turned out to be hexaploid. The coexistence of one majority (4x) and six minority cytotypes (2x, 3x, 5x, 6x, 8x, 9x) was found in one population in central Slovakia and represent the most salient case of ploidy coexistence ever reported. Multivariate morphometrics showed that species identification on the...