Morphological and molecular variation in selected species of Erysimum (Brassicaceae) from Central Europe and their taxonomic significance

•Studies provided diagnostic carpological traits for Erysimum species.•Molecular data indicated distinct taxonomic positions of all problematic species.•The distinctiveness of the species was confirmed by RAPD combined with ITS analysis.•Some morphologically similar species could be treated as cryptic species.

Carpological and molecular variation among the 14 species of Erysimum distributed in Central Europe was examined. Special attention was paid to the group of six wallflowers (E. hungaricum, E. pieninicum, E. wahlenbergii, E. virgatum, E. durum and E. hieracifolium) that are morphologically difficult to distinguish forming a complex taxonomic group. It was found that the sculpturing of seed testa and the micromorphological patterns regarding the surface of silique septum obviously vary among the studied wallflowers, while seed dimensions and shapes overlap and are not adequately informative. The highest carpological dissimilarity was noted between E. cheiri and E. crepidifolium, whereas the taxa in the mentioned taxonomic complex were carpologically very similar, only E. virgatum was slightly different. The molecular techniques used here including SSCP and restriction endonuclease-digested rDNA amplified by PCR and combined with RAPD, strongly support the genetic distinctiveness of all Erysimum species studied. Moreover, the results obtained here indicate that the group of five out of six taxonomically problematic Erysimum species consist of distinct, closely related species and may constitute a complex of cryptic species.