XVI International Botanical Congess

The intrageneric relationships of Podolepis with various chromosome numbers, n=3, 7, 8, 9, 10, 11 and 12, were analyzed using molecular data. The DNA of matK and ITS were sequenced for 18 species of Podolepis and 11 species from related seven genera. Both matK and ITS trees support the monophyly of Podolepis, except P. georgi and P. kendallii. Pairwise sequence divergences among the rest species of Podolepis ranged from 0.08 to 2.06 % for matK and 0.98 to 16.71 % for ITS. The Podolepis is composed of three clades, corresponding to groups, Podolepis, Panaetia and Siemssenia, recognized previously as separate genera based on morphological characters. Asteridea and Pterochaeta appear to be sister genera of Podolepis. All of species are characterized by having myxiogenic cypsela and the number and length of pappus in Podolepis tend to reduce with evolutionary advancement. A chromosome base number of x=12 may be ancestral, with dysploidyal reduction a primary mode of chromosome evolution in the Podolepis.