Variation in the rbcL sequence of Stegnogramma pozoi subsp. mollissima (Thelypteridaceae) in Japan.

Stegnogramma pozoi (Lagasca) K. Iwats. subsp. mollissima (Fischer ex Kunze) K. Iwats. is one of the most common ferns in Japan with a very broad geographical distribution and habitat ranges. We examined the intrasubspecific variation of the rbcL gene, and found three types in the subspecies (Atami-1, Atami-2, and Tateyama types). The Atami-1 and 2 types shared three apomorphic nucleotides and their geographical distribution is intermingled. Thus, we considered them to have intraspecific variation. In contrast, the Tateyama type had 4–5 different nucleotides than the Atami types, and showed a more northern distribution. Leaf morphology of the Tateyama type is distinct from that of the Atami types, though the leaf shape in Tateyama type varies considerably and in some cases overlaps with other types. Ferns have fewer morphological features that are systematically significant than flowering plants because they lack complex reproductive organ. It is reasonable to expect that species recognition of ferns based only on leaf morphology can be fine tuned by molecular features. Variation in the rbcL sequences might be useful as an indication of significant biological units. [ABSTRACT FROM AUTHOR]