| Research Abstract |
Chromosome numbers from 112 populations of 75 species of 30 genera in Gnaphalieae and 8 populations of 6 species of 3 genera in Plucheeae were determined. Although the chromosome base number of Gnaphalieae outside of Australia is constant on x=7, the variable dysploidy series in Angianthus (n=13,12,6), Asteredia (n=9,7), Erymophyllum (n=14,11), Gnephosis (n=11,8), Hyaloserma (n=12,11,8), Lawrencella (n=11,8), Millotia (n=13,11,8), , Myriocephalus (n=14,11), Podolepes (n=12,11,10,8,7,3), Pogonolepis (n=6,5,4), Polycalymma (n=14,8), Pycnosorus (n=10,6), Rhodanthe (n=11,10,8,7,5) and Tricanthodium (n=4,3) were found in Australian semi-desert. To clarify the species relationship and the evolutionary trends in chromosome number habit and morphological characters, we have compared the nucleotide sequences of matK gene of chloroplast between species and constructed the molecular phylogenetic trees of Grapharieae. The matK tree supports the monophyly of the genus Podolepis, except P.kendallii which has onece classified in Herychrysum. The genus Podolepis is divided into 2 clusters corresponding to the difference of habits, perennial and annual. The dysploid reductions from n=12 to n=3, have occurred in two clades and these derived characters are regarded to be adaptive under the arid or seasonally dry conditions.
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