Hybridization between polyploids Cardamine enneaphyllos and C. glanduligera in the West Carpathians: evidence from morphology, pollen fertility and PCR-RFLP patterns

In the present study hybridization between the decaploid Cardamine enneaphyllos and hexaploid C. glanduligera (both previously assigned to Dentaria) was examined. The study area was located in the West Carpathians in Slovakia, where the distribution ranges of the putative parental species overlap, and they occur sympatrically. The putative hybrid C. ×paxiana was studied in many localities in terms of its morphological variation, pollen fertility and PCR-RFLP patterns. Prior to analyses hybrid individuals were tentatively determined based on three morphological characters reported as diagnostic: flower colour, presence of glands on leaves and length of rhizome internodes. Such tentative hybrid identification was confirmed by strongly decreased pollen fertility and an additive restriction pattern in the nuclear ITS region. The possible sources of the substantial morphological variation of hybrids, revealed by morphometric analyses, are discussed. Based on the results of the PCR-RFLP analysis of cpDNA, bidirectional hybridization occurred, although C. enneaphyllos was usually the maternal parent. Geographic distribution and sterility of hybrid individuals suggest that they are repeatedly generated from crosses between the parental species, and represent F1 or early generation hybrids maintained by vegetative reproduction.