Karyotype and AFLP data reveal the phylogenetic position of the Brazilian endemic Hypochaeris catharinensis (Asteraceae)

Abstract

The genus Hypochaeris offers an excellent model for studies of recent adaptive radiation in the South American continent. We used karyotype analysis with chromomycin A3 (CMA3)/4',6-diamidino-2-phenylindole (DAPI) banding and fluorescence in situ hybridization (FISH), and amplified fragment length polymorphism (AFLP) fingerprinting to investigate for the first time the Brazilian endemic H. catharinensis and define its position within the South American group of species. Strong CMA-positive signals were seen at the end of both arms of chromosome 3 and at the end of the long arm of chromosome 4. DAPI bands were only detected in subterminal position on short arm of chromosome 4. FISH with 5S and 35S ribosomal DNA (rDNA) probes revealed a single 5S rDNA locus on short arm of chromosome 2, typical for all other South American Hypochaeris taxa analyzed to date. The 35S rDNA locus was identified at subterminal position on the short arm of chromosome 3, as reported so far for only two of the known species (H. lutea and H. patagonica). The AFLP study included 55 individuals, comprising nine species of the South American Hypochaeris plus their putative ancestor H. angustifolia. Eleven AFLP primer combinations generated a total of 401 fragments, of which 388 (96.7%) were polymorphic. High genetic similarities were observed among taxa, with all South American Hypochaeris species falling into one main cluster [100% bootstrap (BS)]. Hypochaeris catharinensis is closely related to H. lutea (82% BS), forming a well-separated subcluster within the South American species. Taken together, the karyological and AFLP data contribute to the placement of H. catharinensis within the phylogenetic framework of South American species of Hypochaeris and allow the definition of a novel and well-resolved phylogenetic group (the Lutea group).