Abstract
Morphological and cytological variation among populations of Asarum fauriei (Aristolochiaceae) in central and northern Honshu of Japan was examined. Triploid (2m=36) and diploid (2n=24) plants were found widely throughout the geographical range of the species. The chromosome numbers are mostly consistent within a study site, but rarely diploid and triploid plants grew side by side in the same locality, and two different triploid plants distinguishable from each other in leaf and floral aspects occurred in the same locality. The two different triploid plants appear to be of different origin and may have no direct relationships on the basis of morphological differences. Morphologically, all of the floral and leaf characters varied continuously, and no discrete gaps were found among populations. The populations, however, were clustered into three major groups when the data obtained from morphological characters were subjected to principal component analysis. Taxonomically, two of the three groups correspond to two infraspecific taxa, var. fauriei and var. nakaianum, and the other, which is mostly triploid and morphologically characterized by larger ovate leaves and longer calyx lobes relative to calyx tube, may be regarded as a new infraspecific taxon.
