J. Jpn. Bot. 91 Suppl.: 178–200 (2016) A Revision of the Genus Trollius (Ranunculaceae) in Japan Yuichi KADOTA Department of Botany, National Museum of Nature and Science 4–1–1, Amakubo, Tsukuba, 305-0005 JAPAN E-mail: [email protected] (Accepted on September 3, 2016) The genus Trollius (Ranunculaceae) in Japan is taxonomically revised. Plants belonging to the genus predominantly grow in grasslands of montane and alpine zones (higher than 1500 m) in Japan. However, in the lowlands of Hokkaido, northern Japan, Trollius plants were also found along rivers. Among such fluvial plants two species are newly recognized; T. soyaensis Kadota in the Dohoku area and T. teshioensis Kadota extending from the Dohoku to the Doto areas. A new section, sect. Yezoinsulicola Kadota, is proposed based on the two species; T. soyaensis and T. teshioensis. Plants from Rebun Island, northern Hokkaido, have been frequently attributed to the Asian continental species, T. ledebourii Rchb. or T. ledebourii Rchb. var. polysepalus Regel & Tiling, mainly due to the petals being longer than the stamens. However, the petals are somewhat fleshy and are equipped with well-developed nectary pits. The sepals are many in number (7–13) and ascending incurvedly, hence the flowers are bowl-shaped. On the contrary T. ledebourii has patent sepals and the flowers are flat and saucer-shaped. Thus the plants from Rebun Island represent an undescribed species belonging to sect. Insulaetrollius Drosz. distributed in Far East Asia. This new species is described as T. rebunensis Kadota. The plant called ‘Shinano-kinbai’ in Japanese is a representative of Japanese alpine plants. The name Trollius japonicus Miq. has been adopted for this plant. It happens that the type specimen derived from ‘Jeso’ (= Hokkaido, Japan) has follicles with short and straight beaks and developed keels. Thus the type specimen of T. japonicus should be ascribed to T. riederianus Fisch. & C. A. Mey. Consequently a new name, T. shinanensis Kadota, is proposed for ‘Shinano-kinbai’ based on the collection from Mt. Asahi-dake, Itoigawa-shi, Niigata Pref., central Honshu, Japan. In total four sections and eight species are recognized in the genus Trollius in Japan. Key words: New species, new section, Ranunculaceae, sect. Yezoinsulicola, taxonomy, Trollius rebunensis, Trollius shinanensis, Trollius soyaensis, Trollius teshioensis. The genus Trollius (Ranunculaceae) is are characterized by ternate leaves and golden comprised of ca. 30 species (Wang 1979, yellow flowers and resemble each other closely. Kadota 1985) and three species (Kitamura and In the classification of the genus such traits as Murata 1961); four species (Shimizu 1983) or the number of sepals and the relative length of five species or more (Ohwi 1953, Kadota 1987, petals to stamens are traditionally employed. 1991, Shimizu and Kadota 2014) are reported Although the number of sepals is determined from Japan. The constituent species of the genus from herbarium specimens, the direction —178— December 2016 Kadota: Revision of Trollius in Japan 179 (patent vs. ascending) of them is not understood long but non nectariferous petals and the second on the specimen level. It is rather difficult to with relatively short but fleshy and nectariferous comprehend the other properties of the petals (the petals. texture, coloring, and thickening of the blades, the depth of the nectary pits, presence or absence Fluvial Trollius of nectar in the nectary pits) in addition to their Almost all the species of Trollius grow in relative length. Therefore I tried to examine montane to alpine herb stands and begin to living materials in the field and to understand the flower at the earliest in mid-July every year ranges of morphological variations on natural (the flowering period heavily depends on the population level. time of snow thawing). However, I was aware of the occurrence of Trollius populations Petals in the genus Trollius inhabiting streamsides and the early flowering Both Trollius hondoensis Nakai (sect. (in June every year) when I conducted field Longipetala) and T. rebunensis Kadota (sect. work on Cirsium and Saussurea (Asteraceae) in Insulaetrollius) have the petals longer than the Hokkaido. In Japan T. hondoensis exceptionally stamens. The petals of T. hondoensis are long occurs in herb stands of the montane zone but thin and are provided with degenerative (ca. 1500 m in elevation); however, the other nectary pits. As far as was examined, the nectary species (except for T. rebunensis, see below) are pits substantially did not secret nectar. On the alpine plants and live in mesic herb stands of other hand the petals of T. rebunensis are long higher elevations (2000 m or higher). Trollius and thick, somewhat fleshy, and the nectary pits plants generally have low shade tolerance and are enough deep and well developed. Based on they prefer sunny habitats. In Hokkaido such the observation in Rebun Island the nectary pits habitats may be found in alpine meadows of certainly did secret nectar. high mountains and streamsides of low altitudes. In the other two species of sect. Macro- Suitable habitats for them are not the upper petalus, Trollius asiaticus L. (in Altai and reaches of rivers where the water runs fast and Sayan Mountains, Siberia) and T. dshungaricus strongly in torrent but midstream where the Regel (in Tien Shan Mountains, Central Asia), water runs gently during fine weather. Actually the petals were long but thin, and the nectary the lowlands are generally covered with a dwarf pits did not seem to secret nectar. In the sect. bamboo, Sasa kurilensis Makino & Shibata Insulaetrollius it was ascertained that all the (Poaceae), in the Dohoku and the Doto areas, constituent species had nectar-secreting petals Hokkaido, and open habitats without Sasa are regardless of the petal length. Within the sect. exclusively found along streamsides. After Trollius it was observed that the petals were extensive field examinations in Asia, Siberia, somewhat fleshy and nectar was secreted in the Himalayas, and Europe, I have never seen T. altaicus C. A. Mey. subsp. altaicus (in Altai Trollius plants along such a streamside. and Sayan Mountains, Siberia) and subsp. During the time of snow melting the water pulcher (Makino) Kadota (in Rishiri Island, increases considerably in the lowlands of Hokkaido, Japan) and T. europaeus L. (in Hokkaido. The increased volume of water is Pyrenees Mountains). In T. pumilus D. Don, an presumed by the position of litters on branches alpine species of the Himalayas, similar nectar of trees along streamsides. The surface of the secretion was also confirmed in the filed. Based water can be 3 m or higher during the time of on these observations it is considered that there flooding. However, the increase in water due are two groups in terms of attracting insects to snow melting may take place once a year. within the genus Trollius: the first group with Consequently the Trollius plants found along 180 The Journal of Japanese Botany Vol. 91 Centennial Memorial Issue streamsides in Hokkaido are not rheophylic but reddish purple; inhabitants of Rishiri Island fluvial. north of Hokkaido [sect. Trollius] ................ As fluvial species distributed in the ........................... 3. T. altaicus subsp. pulcher lowlands of Hokkaido two new species are 3b. Flowers parabolic to saucer-shaped, recognized as stated below. These two new sepals patent to ascending, usually slightly species, T. soyaensis and T. teshioensis, share overlapping each other; styles and stigmas in common robust plant size. In particular, greenish, not reddish purple ........................ 4 their inflorescences are larger than those of the 4a. Petal blades thin and flat, not thickened in alpine species; flowers of the alpine species the proximal part, acuminate to emarginate, are replaced with inflorescences in the fluvial usually clearly longer than stamens; species, i.e., the inflorescences in the fluvial nectary pits dimple-like; sepals patent [sect. species are compound cymes. This situation is Longipetala] ........................ 4. T. hondoensis similar to the relationships between Anemone 4b. Petal blades thickened in the proximal part, narcissiflora L. subsp. nipponica (Tamura) roundish to truncate, usually shorter than Kadota (flowers solitary) and A. sikokiana or sometimes longer than stamens [sect. (Makino) Makino (flowers several in a cyme; Insulaetrollius] ............................................. 5 Kadota 2006, 2016). This implies that the two 5a. Sepals 5–12, inner sepals ascending, flowers fluvial species of Trollius in Hokkaido may be deep bowl-shaped; petals longer than or primitive based on the evolutionary trends of sometimes as long as the stamens; inhabitants inflorescences. of Rebun Island, north of Hokkaido ............. ................................................ 5. T. rebunensis Key to the Japanese species of Trollius 5b. Sepals usually 5, flowers saucer-shaped; 1a. Pedicels 8–15 cm long, to 20 cm long at petals shorter than or sometimes as long as frutescence; stem usually taller than 100 the stamens ................................................... 6 cm; flowers on axillary inflorescences in 6a. Styles shorter than 2 mm, erect or hooked, additionally to the terminal one, usually more keeled; sepals usually less than 10; petals than 5; fluvial species in the lowlands of usually longer than 10 mm; alpine plants of Hokkaido [sect. Yezoinsulicola] ................. 2 Hokkaido ............................. 6. T. riederianus