Biosystematics of Sino-Japanese pteridophytes

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1. Matteuccia intermedia has been considered to be of hybrid origin and is a key species for understanding the phylogeny of onocleoid ferns. Comparative morphology of pneumatophores and grooves on leaf axes, cytology, and enzyme electrophoresis indicate that the species is a distinct species closely related to Onoclea orientalis.2. Cytotaxonomic studies were made for 90 fern species from Yunnan, southwestern China. They recorded for the first time the basic chromosome numbers of Gymnogrammitis (x=36) and Sorolepidivm (x=c. 35), and confirmed the basic numbers reported so far for most Chinese genera. A cytogeographic study sugested that Chinese fern flora is more diverse and ancestral than the Japanese. Our results also showed that there is a strong correlation between triploids and agamospory, as is known for fern in the other regions.3. Molecular systeamtic studies were made to examine the phylogenetic relationships of pteridophytes and seed plants.(1) The gene map of Adiantum capillus-veneris chloroplast DNA much differs from typical angiosperm chloroplast genome in gene order and organization. At least two inversions and elongation of the inverted repeat is postulated to account for the difference.(2) Maximum likelihood analysis of deduced amino acid sequences of rbcL gene indicates that Botrypus, which has been considered as a progymnosperm, clusters monophyletically with the other ferns, in which the closest relative is Osmunda, and that ferns and seed plants cluster monophyletically, and ferns and bryophytes do not belong to a monophyletic group.(3) Results of a rbcL gne study indicate that extant gymnosperms are monophyletic and not paraphyletic, and in Gnetopsida, Gnetum and Welwitschia are more closely related to one another thar either to Ephedra.