ワタムキアザミとヒダアザミの形態的変異と分布

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Cirsium tashiroi and C. hidaense, which are closely related to each other, are distinguished from one another by the following characters: in the former, radical leaves sessile, incised or divided, cauline leaves subamplexicaul, involucres about 1 cm wide; in the latter, radical leaves long-petiolate, entire with spines on the margin, cauline leaves not amplexicaul, involucres 1.5 to 2 cm wide. However, many plants having intermediate forms have been observed in some natural populations. We investigated variation of these characters in their natural populations. The plants were collected with quadrat or line-transect method at the sites shown in Table 1. for analysis of radical leaf shape, leaf length (1), petiole length (p), width from the midrib to the margin in the widest part of the leaf (c) and width from the midrib to the margin in the most narrow part just above the part of c (d) (Fig. 1) were measured. For comparison of involucre size, length (a) and width (diameter in the widest part) (b) of the involucres were measured in the fresh heads (Fig. 1). Almost all plants had sessile or very short-petiolate and incised to devided radical-leaves (Cirsium tashiroi) in some populations had long-petiolate and serrate radical-leaves (C. hidaense) in the others, although a few plants might have the radical leaves which were divided in the lower part and serrate in the upper part (the intermediate forms) (Figs. 2, 4). The other populations contained all kinds of the plants (Fig. 4). Many upper cauline leaves on the plants with radical leaves of the intermediate forms and some highest leaves also on the plants of Cirsium hidaense were sessile and subamplexicaules. Distinctive correlation between the leaf shape and the size of the involucres was not recognized. And mean values of the size of involucres were variable among the populations (Table 2). The populations of Cirsium tashiroi are geographically distributed from Shiga Pref. eastwards to the western part of Shizuoka Pref., which is the same area as The Central Honshu defined by Kitamura (1934). Those of C. hidaense are distributed only eastern half of the Central Honshu. All populations investigated of the two species including intermediate forms are altitudinally distributed from 300 to 1100 m.
1988-06-25

ワタムキアザミとヒダアザミの形態的変異と分布

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