Taxonomic and Phylogeographic Studies of Chrysosplenium macrostemon s.l.(Saxifragaceae)

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This study aims to reexamine taxonomically Chrysosplenium macrostemon s.l. distributed widely in Pacific Ocean side of Honshu, Shikoku and Kyushu, through the morphological and cytological observations and the molecular phylogenetic analyses. The results obtained are as follows :1.The monopyly of C.macrostemon s.l. was suggested from the analysis of ITS sequenses of rDNA in 43 populations covering 5 species of Ser.Macrostemon (23 populations of C.macrostemon, 6 of C.echinus, 5 of C.fauriae, 4 of C.nagasei, 5 of C.kiotense), and sister group of C.macrostemon s.l. was also suggested to be C.echinus.2.Phylogenetic analysis based on ETS sequences of rDNA was performed in 51 populations of C.macrostemon using C.echinus as its outgroup. The 27 ETS sequence types were recognized. The phylogenetic tree among these types showed that the populations around Itsuki-mura in Kumamoto Prefecture diverged first and the other populations formed a clade. This clade formed polytomy as a whole, and phylogenetic relationships among populations within this clade were obscure.3.One kind of ETS sequence type (Type 4) within the clade was common to 22 populations distributed widely in Kyushu, western part of Shikoku, Kii Peninsular, and Tanzawa Mountais in Kanagawa Prefecture. However, the floral and seed morphology in these populations was very diversified, which suggests that genetic and morphological diversification are not necessarily concordant.4.Chromosome number of C.macrostemon was 2n=22(diploid) in all of 43 populations so far analyzed, and no polyploidy seems to occur in this species.5.Hereafter, the molecular phylogenetic analyses including ITS sequences and the observation of floral and seed morphology in more populations are needed for making a clear conclusion along the purpose of this study.