Phylogeny of Aspleniaceae Inferred from rbcL

We determined rbcL sequences of 25 species and 2 varieties of Aspleniaceae with various leaf and rhizome morphologies, and conducted a phylogenetic analyses with the following conclusions: 1) leaf shape is not congruent with rbcL phylogeny in Aspleniaceae; 2) rhizome morphology (erect-ascending or creeping) reflects rbcL phylogeny; 3) naturally occurring hybrids are generated only between closely related species and thus reflect the rbcL phylogeny. The third conclusion was especially well-supported by our allozyme analyses of hypothesized hybrids be- tween distantly related species of Aspleniaceae. A popular cultivated fern hybrid in Japan, As- plenium xkenzoi, is believed to be a hybrid between A. prolongatum and A. wrightii, which are distantly related in our molecular tree. However, our allozyme analysis of A. xkenzoi showed that it is a hybrid between A. antiquum and A. prolongatum, whose close relationship was first suggested by our rbcL tree. Thus, A. xkenzoi appears to to be a hybrid between two closely related species with very different morphologies. Aspleniaceae are a well-defined family of leptosporangiate ferns, character- ized by an elongate sorus type along the leaf veins with an elongate indusium, X-shaped leaf traces in the upper parts of fronds, clathrate rhizome scales, and a basic chromosome number of x = 36. However, intrafamiliar relationships of the Aspleniaceae are poorly known and no widely accepted system of clas- sification for the family has been established (Iwatsuki, 1975; Tryon and Tryon, 1982). More than 700 species currently belong to one genus, Asplenium L., although various authors have segregated some species of Asplenium into dif- ferent genera such as Phyllitis Newm., Camptosorus Rupr., Neottopteris J.Sm., Boniniella Hayata, and Hymenasplenium Hayata. The status of these genera is too obscure to be widely accepted because the relationship to other members of the Aspleniaceae is not clear. In this study, we determined the rbcL sequences of 25 species of Aspleni- aceae with various leaf and rhizome morphologies and conducted a molecular phylogenetic analysis in order to elucidate intrafamiliar relationships. A mo-