Phylogeny of Osmundaceae inferred from rbcL nucleotide sequences and comparison to the fossil evidences

We determined rbcL sequences of 11 of 15 extant species of Osmundaceae which represent all three genera, Osmunda, Todea and Leptopteris. Our phylogenetic analysis concluded: 1) Osmunda subg. Osmunda and subg. Plenasium are monophyletic groups, but subg. Osmunda strum is not. The genus Osmunda is not monophyletic because Todea and Leptopteris are positioned within Osmunda. 2) Osmonda cinnamomea is the most basally positioned species in Osmundaceae, and it can be called as "a living fossil" because a fossil species (O. claytoniites) with almost the same morphology as this species was recorded from the Triassic. 3) Osmunda japonica and O. regalis are very closely related with only one nucleotide difference in the rbcL gene. 4) Greater nucleotide variation (5-7 nucleotides) was found between conspecific samples of O. cinnamomea and O. claytoniana collected from Japan and United States. Each of these two species may comprise more than two biologically differentiated species.