A phylogenetic analysis and new delimitation of Senecio sect. Crociseris (Compositae: Senecioneae), with evidence of intergeneric hybridization

Senecio sect. Crociseris is one of the three main sections of western Eurasian/northern African Senecio species. Previous studies indicated that species commonly assigned to this section are closely related to those of sect. Doria. The aim of the research presented here was to test the morphology-based delimitation of sect. Crociseris using phylogenetic analyses of plastid and nuclear DNA sequence data. The results of these studies are used to propose a new delimitation of sect. Crociseris. Species of sect. Doria were nested within a clade formed by species of sect. Crociseris. Section Doria is therefore best considered a synonym of sect. Crociseris. In addition, S. racemosus, traditionally included in sect. Crociseris, is transferred to the genus Jacobaea. One of the two J. kirghisica specimens that were sequenced contains ITS copies that are most closely related to those of sect. Crociseris as well as copies that nest among ITS accessions of Jacobaea. This suggests intergeneric hybridization between Senecio and Jacobaea.