Morphology mirrors ploidy and reproductive modes in Pilosella officinarum

Abstract

Pilosella officinarum is represented predominantly by tetraploid (2n = 36), pentaploid (2n = 45) and hexaploid (2n = 54) cytotypes reproducing, to various degrees, both sexually and apomictically. Its current intraspecific taxonomical treatment is based mainly on selected apomictic lineages, the large number of which makes the treatment confusing and not generally applicable. We therefore tested the breeding modes of a representative set of plants from central Europe, cultivated under experimental conditions. Each ploidy level was associated with a different reproductive pattern (4x – sexual, 5x – prevalently apomictic and 6x – sexual and apomictic). Whereas sexual tetraploids occurred in the western part of the study area (the Czech Massif), apomictic pentaploids and hexaploids were scattered in its eastern part (Western Carpathians and Pannonia). Moreover, the hexaploid cytotype formed a distinct exclusively sexual group restricted to steep river canyons of the Czech Massif. Morphometric analyses were performed to determine the set of characters which distinguish major lineages characterized by different ploidy and reproductive modes. Their results confirm the existence of morphological differences between plants of different ploidy levels and, in the case of the hexaploid cytotype, different modes of breeding. Knowledge of ploidy and reproductive modes is therefore essential for elucidating the reticulate infraspecific structure of Pilosella officinarum.