Some species of Ophioglossaceae, such as Ophioglossum petiolatum, O. thermale and Ophioderma pendula have very simple gross morphology, and all are widely distributed in the Old World. Several different biological species might be contained in these species due to the lack of good taxonomic characters. In this work, we made detailed analysis of the intraspecific rbcL sequence variation of the above three species from various localities. Although rbcL is known as a slowly evolving gene, we found large amount of variation in all the three species. We will also discuss interspecific phylogeny of the Ophioglossaceae based on the same sequence data.

Key words: intraspecific variation,molecular phylogeny,Ophioglossum,pteridophyte,rbcL