2026-07-09 九州大学
両植物とも葉や花弁の長さが1cmにも満たないミニチュア植物であり、外見は極めてよく似ているが、遺伝解析の結果より、別の種より進化した他人の空似であったことが明らかになった。
＜関連情報＞
- https://www.kyushu-u.ac.jp/ja/researches/view/1515
- https://www.jstage.jst.go.jp/article/apg/77/2/77_202517/_article
屋久島産オトギリソウ属（オトギリソウ科）の分類学的改訂、および新種小型種Hypericum yaedakenseの発見 Taxonomic Revision of Hypericum (Hypericaceae) on Yakushima, Japan, with a New Miniaturized Species, H. yaedakense
Daiki Takahashi, Yoshihisa Suyama, Naoko Ishikawa, Masaya Yamamoto, Tomoko Fukuda, Takuro Ito, Kana Magota, Koji Yonekura, Tetsukazu Yahara
Acta Phytotaxonomica et Geobotanica Published: June 30, 2026
DOI:https://doi.org/10.18942/apg.202517
Abstract
Yakushima is an island known as a biodiversity hotspot for vascular plants in the Japanese Archipelago. At high-elevation areas of Yakushima, three miniaturized groups of Hypericum sect. Hypericum (Hypericaceae) are known. They are distinguished by gland characteristics of the leaf lamina: Group I having only pellucid glands, Group II with both pellucid and dark glands, and Group III with only dark glands. To further distinguish these three groups, we analyzed the phylogenetics, population genetics, morphology and flow cytometry. Genetic analyses showed that Groups I and III are not closely related and clearly differentiated. In addition, individuals of Group II showed intermediate genetic and morphological characteristics of the other two groups. The three groups also differ in ploidy levels; Groups I, II, and III are tetraploid, triploid, and diploid, respectively. These findings suggest that Groups I and III represent two distinct species that may have independently evolved into miniaturized forms on Yakushima, while Group II represents their F1 hybrids. Based on this evidence, we describe Group III as a new species, H. yaedakense D.Takah. & Yahara, and propose a new combination, H. kiusianum Koidz. var. lucidum (Y.Kimura) D.Takah., for Group I.
