TML> Yatabe, Yoko* and Noriaki Murakami. Cytotaxonomical and enzyme electrophoretic data have discovered several cryptic species in various lineages of homosporous ferns (Paris et al., 1989). We are trying to establish new method to recognize such cryptic species more efficiently. Chloroplast DNA sequences may provide us with favorable information because of its advantageous feature as a molecular marker. We examined rbcL sequences in various fern species and found a large amount of variations among conspecific materials. Considering the slow evolutionary rate of rbcL (7x10-8 nucleotide substitution per year on average), the large amount of rbcL sequence variation within a single morphological species may suggest that it contain several cryptic species. Especially, in bird-nest fern, Asplenium nidus sensu Holttum (1974), the difference of rbcL sequences between most distantly related individuals reached 4-5% (Murakami et al. 1999). In the sympatric populations of A. nidus of Mt. Halimun National Park, West Java, Indonesia, we found five rbcL sequence types. The phylogenetic analyses, including the plants from other localities, indicated that these five rbcL types are not closely related to each other in A. nidus complex. From our ecological observation, these five rbcL types turned out to be differentiated in their habitat preference. These rbcL types were genetically differentiated also in their nuclear genomes when we examined allozyme polymorphism. These results strongly suggest that these rbcL types are separate biological species. Moreover, crossing experiments were performed among various pairs of rbcL types, including allopatrically distributed pairs as well as sympatrically distributed ones. As the results, it was revealed that hybrids failed to form between many pairs of the rbcL types and they are reproductively isolated. It was shown that rbcL is an efficient first key to find cryptic species.

Key words: Asplenium nidus , rbcL , cryptic species, Fern