The taxonomic history of Pilosella floribunda (Asteraceae), a common hybridogenous aggregate of central, northern and eastern Europe

The taxonomic history, nomenclature and application of one of the oldest species names in Pilosella are reviewed. Hieracium floribundum originally included a hybrid swarm with the participation of Pilosella lactucella, P. caespitosa, P. praealta and partly P. officinarum, and was interpreted either as a binary (P. lactucella × P. caespitosa) or triple (P. lactucella × P. caespitosa × P. praealta) hybrid. The original material of H. floribundum from Silesia, Poland includes plants of the triple hybrid which are designated as its lectotype in conformity with the usage of the species name that has been predominant during its history. The lectotype belongs to a morphotype in which the diagnostic characters of P. lactucella are dominant, and which is not typical of northern and eastern Europe. A further lectotype from the same hybrid complex is designated for H. floribundum var. subcymosum.