Taxonomical value of inflorescence scent in Hieracium s. str.

In Central Europe Hieracium s. str. comprises a vast number of mostly apomictic taxa presumably originated from hybridization in the past. Inflorescence scents of 37 taxa from 7 sections of Hieracium subgenus Hieracium were investigated by headspace analysis. Overall, 58 different scent compounds belonging to benzenoids, sesquiterpenes, homoterpenes, monoterpenes and fatty acid derivatives were found. The scent patterns were used to perform a neighbour joining and reticulation analysis and the results are discussed against the background of current taxonomy. The scent clustering revealed a clear segregation between sections Drepanoidea, Tridentata and Hieracioides against members of the sections Hieracium, Oreadea and Bifida. The scent tree reflected distinct morphological and phenological groups in Hieracium and were congruent with actual genetic groupings. Actual section circumscriptions were supported with some exceptions concerning the sections Oreadea and Vulgata. Reticulation analyses of scent data reflected the hybrid status of intermediates, such as Hieracium franconicum, Hieracium caesium, as well as taxa of Hieracium wiesbaurianum and Hieracium glaucinum. The data also pointed towards a hybrid origin of members of some putative non-hybrid taxa such as Hieracium lachenalii, which is in accordance with recent molecular studies. The taxonomical usefulness of scent data in dominantly apomictic taxa is discussed. (C) 2011 Elsevier Ltd. All rights reserved.