オーストラリア半砂漠地域へのキク科植物の適応進化の解析

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We have collected about 120 population samples of Asutralian Astereae and Gnaphalieae and investigated their habitat condition during the field expeditions (from Sept.21 to Oct.30 for Victoria, New South Wales, Qeensland, Northern Territory and South Australia). All of collections, except the donating speciments to Australian State and National Harbaria, have been brought back to Japan and served to the following researches. Chromosome numbers from 103 populations attributed 68 species of 23 genera of Gnepharieae and from 8 populations attributed 6 species of 3 genera of Pulcheeae were determined. The frequent dysploidy has been found in Gnaphalieae although the basic chromosome number x=10 is conservative in Pulcheeae. They are in Podolepis (n=12-3) , Pogonolepis (n=6-4) , Rhodanthe (n=11-5) , Tricanthodium (n=4-3) and so on. Species of arid regions frequently display an annual habit. To clarify the species relationship between species and the evolutionary trends in Chromosome number, habit and morphological characters adapting to the Australian arid regions, we have compared the nucleotide sequence of matK gene of chloroplast and constructed the molecular phylogenetic trees in Brachyscome. Both trees are consistent the support the monophyly of these genera. Brachyscome is divided into 4 clusters corresponding to the morphology of anther appendage and style, geographical distribution and the variation pattern of chromosome number. The dysploid reductions from n=9, the change of habit from perennial to annual and the change of fruit morphology from simple to complex have been derived in several independent leneages and are regarded to be adaptive in arid or seasonally dry conditions. Karyotype analyzes were made on 68 taxa of Brachyscome and 8 species of 7related Australian Astereae genera.