Studies on the relationship between genetic diversity within the fungus that specifically occur on Fagus crenata supule and its host distribution.

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To search for major factors that affected fungal distribution, ITS sequence diversity of Dasyscyphella longistipitata(Hyaloscyphaceae, Helotiales, Disomyoate, Ascomycota) that occur on Fagus crenata cupulus obtained from wide areas in Japan were compared. Five to 20 cupules were collected every 5m apart at each sampling site, and single-spored isolates were obtained. In 120 isolates obtained from 12 sites, 38 haplotypes were detected, and the haplotype H12(43% of the total isolates) was detected from all the populations. In addition, H28(15%) and H10(10%) consisted of the three major haplotypes. These three haplotypes were placed in inner clades in the haplotype network based on statistical parsimony. Nested clade analysis did not indicate geographic isolation. Analysis of molecular variance attributed the genetic diversity for the diversity within the population. Genetic distance was not found to be correlated with geological distance, and no relationship was found with the phylogenetic grouping of the host. These facts suggested the whole the populations of D.longistipitata Japan form a large continuum. However, genetic diversity was higher in south-western areas and north eastern areas in Japan. This genetic distribution pattern suggests that the current population initiated from the ancestral population in the glacier period with high genetic diversity in south-western Japan, followed by the continuous expansion along with the host expansion, decrease of the genetic diversity in the middle Japan due to the extinction of the host, while keeping diversity due to continuous distribution of the host in the north-east Japan.