オオバコ属植物の種生物学的研究 : 1.トウオオバコ並びに近縁種の変異とその類縁
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概要
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The geographical distribution, ecology, and morphological variations of three native and one introduced taxa of Plantago belonging to Section Plantago (sensu WAGENITZ, 1975), i.e. Plantago asiatica, P. japonica, P. togashii and P. major, were critically investigated based on materials collected from the field and deposited in the Herbaria (TI, KYO and SAPT), and further, the taxonomic status of these taxa was re-evaluated in the light of evidence obtained in the present study. As a result, it became evident that P. togashii, which has thus far been regarded to be an endemic species in the coastal grasslands and gravel barrens of Hokkaido, is conspecific with P. japonica, which occurs in the coastal habitats of Honshu. P. japonica (including P. togashii) is a very variable species, but it is characterized by its extremely robust growth habits; it possesses large, thick coriaceous leaves, attaining 56.6 cm in length and 18.0 cm in width, and also long spikes often exceeding 70 cam in height. It was also found that this species produced mean seed numbers of 8.7-13.7 per capsule, ranging from 5 (minimum) to 17 (maximum). Seeds are small, 1.0-1.3 mm in mean length, and 0.6-0.7 mm in mean width, with characteristically elevated and striped ornamentation as observed by SEM. Both plants referred to P. japonica collected from Honshu and those of P. togashii (in the classical sense) collected from Hokkaido were found to be diploid with 2n=12 somatic chromosomes and to possess similar karyotypes (MATSUO and NOGUCHI, 1989). Another closely related species, P. major, also occurs in Hokkaido and northern as well as central Honshu; it was, however, without doubt introduced and naturalized, possibly from Europe. Because of the fact that P. major (diploid with 2n=12 chromosomes) produces mean seed numbers of 8.6-12.2 per capsule, ranging from 4 to 24, and seeds ranging from 1.3-1.4 mm in mean length and 0.8 mm in mean width, the Japanese maritime species, P. japonica (incl. P. togashii), which possesses very similar seed characters, was once considered to be conspecific with European P. major, i.e., P. major var. japonica (FRANCH. et SAVAT.) MIYABE. However, as described above, P. japonica is, as shown by its characteristic vegetative as well as other reproductive traits, a unique maritime species occupying salt-marsh grasslands or gravel barrens and thus possessing a entirely different ecological niche. Another native plantain species, P. asiatica, is a tetraploid with 2n=24 chromosomes (MATSUO NOGUCHI, 1989), and is characterized by much smaller seed numbers per capsule, ranging from 4.5 to 5.9 on the average, and much larger seed size, 1.3-2.0 mm in length ×0.8-1.0 mm in width.
- 日本植物分類学会の論文
- 1989-07-30