Karyological and morphological differentiation of the Tanacetum corymbosum group (Asteraceae) in the Slovak part of the Carpathians

The paper aims to provide a comprehensive overview of karyological and morphological variability of the Tanacetum corymbosum group in Slovakia. We estimated DNA ploidy level and relative DNA content of 530 individuals (45 populations) using DAPI flow cytometry. The morphological variation was studied by univariate as well as multivariate morphometric based on 10 morphological characters of 351 individuals (39 populations). In addition, two characters were measured on 120 achenes (six populations). Flow cytometry analyses confirmed two predominant cytotypes within T. corymbosum group in Slovakia: diploids corresponding to T. clusii and tetraploids corresponding to T. corymbosum . Further, we recorded rare occurrence (1.3% of the dataset) of minority cytotypes – presumable triploids and pentaploids, probably originating from fusion of reduced and unreduced gamete in single species populations. One triploid plant found at the only one locality with common occurrence of T. clusii and T. corymbosum is most probably of hybrid origin. Morphological analyses showed that T. clusii and T. corymbosum could not be clearly distinguished by either of the studied characters but by combining all studied quantitative characters of stem, leaves, and corymbs, it was possible to correctly classify more than 91% of the plants. Number and size of stem leaves as well as capitula, and coloration of the margin of the involucral bracts were identified as the most useful for their determination. Based on revealed karyological and morphological differentiation of T. clusii and T. corymbosum , we favour to recognize them as two separate species rather than subspecies. A key for identifying native Tanacetum species in Slovakia is presented.