Taxonomic revision of Sorbus subgenus Aria occurring in the Czech Republic.

Results of a taxonomic revision of Sorbus subg. Aria occurring in the Czech Republic are presented in a central-European context. Flow cytometry and multivariate morphological analyses were employed to assess the taxonomic diversity within the group. Diploid, triploid and tetraploid taxa were detected. Diploids are represented by a single species, Sorbus aria, which is morphologically very variable. This extensive variability is specific to this species and separates it, among other characters, from polyploid taxa. An epitype for S. aria is designated here. In the Czech Republic, S. aria has been recorded only in southern Moravia, and published records from Bohemia relate to other polyploid taxa of the subg. Aria. Native occurrences previously recorded for S. austriaca and S. carpatica in the Czech Republic are erroneous and relate to individuals of S. aria with lobed leaves. Three new triploid species are described: S. cucullifera M. Lepší et P. Lepší from the Podyjí and Thaytal National Parks between the towns of Znojmo and Vranov nad Dyjí, and S. moravica M. Lepší et P. Lepší and S. pontis-satani M. Lepší et P. Lepší from the Moravian Karst area near the city of Brno. Tetraploid taxa include S. danubialis and two newly distinguished taxa: S. thayensis M.Lepší et P. Lepší and S. collina M. Lepší, P. Lepší et N. Meyer. Sorbus thayensis is endemic to the Podyjí and Thayatal National Parks and in a similar manner as a triploid species varies very little morphologically, which indicates that these polyploid taxa reproduce apomictically. All these new species are assumed to have originated from interbreeding between S. danubialis and S. aria. Up until now, Sorbus collina has been referred to as S. aria in the Czech Republic, as S. pannonica in Germany and as S. graeca in Austria and Hungary. Records referring to S. graeca in southern Moravia (Czech Republic) do not belong to S. collina, but are untypical individuals of S. danubialis. In the Czech Republic, S. collina occurs in central and north-western Bohemia. Sorbus danubialis is confined to central and north-western Bohemia and southern Moravia, and is taxonomically uniform. Old records of the existence of diploid individuals of S. danubialis in Bohemia are incorrect. Detailed distribution maps for all stenoendemics, photographs of the type specimens and line drawings of all polyploid species known from the Czech Republic are presented.