Morphological variation and taxonomy of thePoa macrocalyx complex (Poaceae) in Hokkaido

Abstract

Morphological features of 41 local populations of thePoa macrocalyx complex from the seasides of Hokkaido were analyzed with special reference to the following seven characters: spikelet length, number of florets per spikelet, relative length of side nerves to the entire length of the first glume, that of the second glume, length ratio of the second glume to a spikelet, ratio of length of the closed part vs. entire length of leaf sheaths, and scabrousness of panicle branches and pedicels. All of these characters varied continuously, and considerable degrees of variability within a population were observed. However, separation of populations into three groups became evident when the data were subjected to principal component analysis and also to a method of examination which was devised for identification of a population (not an individual) of this complex. The three groups that resulted from morphological studies were exactly in parallel with the grouping of populations supported by differences of chromosome numbers and geographical distribution. Evolutionary differentiation of this complex was discussed in connection with polyploidy and gametophytic apomixis. As a result of taxonomic considerations, the plants were arranged in three emended varieties of one species:Poa macrocalyx var.fallax, P. m. var.tatewakiana, P.m. var.scabriflora.