MOLECULAR PHYLOGENY OF THE GENUS HYPOCHAERIS USING INTERNAL TRANSCRIBED SPACERS OF NUCLEAR RDNA - INFERENCE FOR CHROMOSOMAL EVOLUTION

Sequences of the internal transcribed spacers (ITSs) of 18S-26S nuclea r ribosomal DNA were used to resolve phylogenetic relationships and ch romosomal evolution among 14 species of the genus Hypochaeris (Asterac eae). Parsimony analysis was performed for phylogenetic reconstruction , and sequence divergence between species was estimated. Pairwise sequ ence divergence within Hypochaeris genus ranged from 0% to 25.68% in I TS1 and from 0% to 17.08% in ITS2. A highly resolved strict-consensus tree was obtained that showed the phylogenetically useful information of ITS sequences within the genus Hypochaeris. Four clades could be we ll distinguished, one of them formed by the single species H. robertia , which appeared to be the most related to the ancestral species of th e genus. The results agree with taxonomic classification based on morp hological data, and the tree obtained, when indels are coded as missin g data, aggregates the species having the same chromosome number, exce pt in one clade. According to the ITS phylogenetic tree, the chromosom al evolution within the genus Hypochaeris conflicts with the previous hypothesis and suggests that karyotype evolution in Hypochaeris was ac companied with both decreasing and increasing dysploidy, probably with several chromosomal rearrangments, and from an ancestral basic chromo some number of 4 or 5.