Biosystematic Studies on Maianthemum (Liliaceae-Polygonatae) VI. Variation in Gross Morphology of M. bifolium and M. canadense with Special Reference to Their Taxonomic Status

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The variability in gross morphology of two species of Maianthemum, namely, M. Bifolium of Eurasia and M. canadense of central and eastern North America, is illustrated in this study with particular emphasis on the variations in quantitative characters. A comparison of the three species of Maianthemum, including an amphi-Pacific species, M. dilatatum (=M. kamtschaticum auct.) is also made, based upon all the available information, and their taxonomic status is discussed.
Considering their close resemblance in gross morphology, their karyotypic and ecological similarities, these three species are evidently closely related, but they can at the same time be regarded as distinct species which exhibit almost complete allopatry and each of which has conspicuous diagnostic characters. Of the three species, however, M. dilatatum is the most variable one and consists of three discrete geographic population groups.
It is to be considered that polyploidy has apparently not played a significant role in the speciation of the genus Maianthemum. Most clones cytologically investigated thus far by various authors have a diploid somatic chromosome number of 36, although occasional triploid (2n=54), tetraploid (2n=72), and other chromosome numbers (2n=64-70) have been reported in plants of the above three species. Such cytotypes are now considered to be of autopolyploid origin, which have arisen spontaneously within or at marginal areas of their distribution range.