国立科博専報，（47）： 417–434，2011年4月15日 Mem. Natl. Mus. Nat. Sci., Tokyo, (47): 417–434, April 15, 2011 Geographical Variation of Astilbe (Saxifragaceae) Species Distributed in Fossa Magna and the Adjacent Regions in Japan Shinobu Akiyama Department of Botany, National Museum of Nature and Science, 4–1–1 Amakubo, Tsukuba-shi, Ibaraki 305–0005, Japan E-mail: [email protected] Abstract. The distribution pattern of Astilbe species distributed in Fossa Magna and the adja- cent regions in Japan is discussed in relation to the differentiation. A new taxonomic treatment of Astilbe in this region is attempted, and a new combination, A. odontophylla Miq. var. okuyamae S. Akiyama is proposed. Key words: Astilbe, distribution, Fossa Magna region, geographical variation, new combina- tion. Gray, A. microphylla Knoll, A. thunbergii (Sie- Introduction bold & Zucc.) Miq.(var. thunbergii), A. hachijo- The genus Astilbe (Saxifragaceae) is distribut- ensis Nakai (A. thunbergii var. hachijoensis (Na- ed disjunctively in East Asia and North America kai) Ohwi), A. okuyamae H. Hara (A. thunbergii and diversified in former. In Japan endemic spe- var. okuyamae (H. Hara) Ohwi), A. formosa (Na- cies and varieties are known and its taxonomic kai) Nakai (A. thunbergii var. formosa (Nakai) treatment has been proposed by several research- Ohwi), A. fujisanensis Nakai (A. thunbergii var. ers (Hara 1939; Ohwi 1953, 1975, 1982; Kitamu- fujisanensis (Nakai) Ohwi), and A. odontophylla ra and Murata, 1961; Ohba 1982, 2001). Miq. (A. thunbergii var. congesta H. Boissieu). Fossa Magna region (Maekawa 1949) is known Among them five taxa, A. simplicifolia, A. hachi- as a floristic region in Japan, which is rich in the joensis, A. okuyamae, A. formosa, and A. fujisan- endemic species especially neoendemic. In Fossa ensis, are endemic to Fossa Magna and the adja- Magna and the adjacent regions nine taxa of As- cent regions. The taxonomic treatment of these tilbe are distributed: these are A. simplicifolia five taxa have been diverse (Table 1). Their opin- Makino, A. japonica (C. Morren & Decne.) A. ions can be summarized into the following two: Table 1. Treatment of the species of Astilbe in Fossa Magna and the adjacent regions Kitamura and Hara (1939) Ohwi (1953) Ohba (1982) Ohba (2001) Murata (1961) A. simplicifolia A. simplicifolia A. simplicifolia A. simplicifolia A. simplicifolia A. hachijoensis A. thunbergii A. hachijoensis A. thunbergii A. hachijoensis var. hachijoensis var. hachijoensis A. okuyamae A. thunbergii A. thunbergii A. thunbergii A. okuyamae var. okuyamae var. okuyamae var. okuyamae A. formosa A. thunbergii A. formosa A. thunbergii A. formosa var. formosa var. formosa A. fujisanensis A. thunbergii A. thunbergii A. thunbergii A. thunbergii var. fujisanensis var. fujisanensis var. fujisanensis var. fujisanensis 418 Shinobu Akiyama one is that local variations are recognized as dif- species still has an ancient character. In Astilbe ferences of species; the other is that some of these other species have leaves (1--)2--3(--4) times ter- are treated as infraspecific taxa of A. thunbergii. nately divided, but in juvenile stage leaves are Hara (1939) recognized all of the taxa concerned more simple. In A. thunbergii var. thunbergii col- as distinct species. On the other hand except A. lected in Mts. Tanzawa, an adult plant with flow- simplicifolia Ohwi (1953) treated four taxa, A. ers has ternate leaves 3--4 times (Fig. 3d), while hachijoensis, A. okuyamae, A. formosa, and A. fu- juvenile plants have simply ternate leaves (Fig. jisanensis, as the varieties of A. thunbergii. Kita- 3e). The simple leaf of A. simplicifolia is consid- mura and Murata (1961) treated A. simplicifolia, ered to be neotenous derivation as pointed by A. hachijoensis, and A. formosa as distinct spe- Takahashi and Hasegawa (2001). Takahashi and cies but regarded A. okuyamae and A. fujisanensis Hasegawa considered A. simplicifolia to be primi- as varieties of A. thunbergii, i.e. A. thunbergii var. tive, however the species with derived character okuyamae and A. thunbergii var. fujisanensis. through neotenous change should be regarded as Ohba (1982) principally followed Ohwi’s treat- derivative. At present it is difficult to give more ment, but later he treated A. hachijoensis, A. strict detection to the species whether primitive or okuyamae, and A. formosa as distinct species derivative, but it is reasonable to recognize this as (Ohba 2001). a distinct species in having unique and consistent To clarify the entity of these five taxa, this pa- morphological characters. per aims to discuss the distribution pattern along with the morphological characters. Astilbe fujisanensis Nakai Astilbe fujisanensis is described by Nakai (1926) based on the specimens from Mt. Fuji. Materials and Methods Later the species is confirmed to occur also sever- To collect the data of the geographical distribu- al other sites in Fuji-Hakone region (Figs. 1b, 4) tion in Fossa Magna and the adjacent regions and grows in higher elevations than A. thunbergii field surveys were made from 2006 to 2009. The var. thunbergii. Astilbe fujisanensis characterized data were also obtained from the herbarium speci- by the lustrous biternate to triternate leaves with mens deposited in KPM, KYO, TI, TNS. All ma- roughly incised double serrations (Fig. 3f). The terials obtained were dotted on the maps. Mor- shape of leaflet with roughly incised double serra- phological features proper to each taxon were tion is similar to the simple leaf of A. simplicifo- compared. lia. Though phylogenetic relationship is not yet clear, the morphological characters of leaves of this species is similar to those of A. simplicifolia. Results and Discussion The distribution range of A. fujisanensis includes Astilbe simplicifolia Makino that of A. simplicifolia, but these two species are This species is described by Makino (1893) on not found in the same places owing to their dif- the collection from Mts. Tanzawa (Okuyama ferent preference of habitat: Astilbe fujisanensis 1952). This species is distributed in Fuji-Hakone grows on soils in open situations while A simplic- region, south side of Mt. Fuji, Mts. Hakone, and ifolia on rocks in semishaded situations. This spe- Mts. Tanzawa (Fig. 1a) and characterized by the cies is sometimes treated as the variety of A. unique simple (not compound) leaves (Fig. 2). thunbergii (e.g. Ohba 2001), but no evidence The simple leaves with roughly incised double clearly supporting their relationship is found. serration are sometimes slightly 3-lobed in larger ones (Fig. 3a & b) or not lobed (Fig. 3c). Taka- Astilbe hachijoensis Nakai hashi and Hasegawa (2001) wrote that this simple This species, described by Nakai (1919) on the leaf is considered to be a kind of neoteny and this collection from Hachijo-jima Island, is confirmed Geographical Variation of Astilbe 419 Fig. 1. Distribution of Astilbe in Fossa Magna and the adjacent regions. a, A. simplicifolia; b, A. fujisanensis; c, A. hachijoensis; d, A. formosa; e, A. okuyamae; f, A. odontophylla. 420 Shinobu Akiyama Fig. 2. Astilbe simplicifolia Makino. Kanagawa Pref., Mt. Tanzawa (T. Ikeda, Aug. 1951, TNS). Geographical Variation of Astilbe 421 Fig. 3. Leaves and terminal leaflets of Astilbe. a, Adult leaf of A. simplicifolia; b and c, juvenile leaves of A. simplicifo- lia; d, adult leaf of A. thunbergii (var. thunbergii); e, juvenile leaf of A. thunbergii (var. thunbergii); f, adult leaf of A. fujisanensis; g, adult leaf of A. hachijoensis; h, adult leaf of A. okuyamae, i, juvenile leaf of A. okuyamae; j, adult terminal leaflet of A. okuyamae; k, adult terminal leaflet of A. odontophylla. Scale indicates 5 cm for b, c, e and i, 10 cm for a and f, and 20 cm for d, g, h and k. 422 Shinobu Akiyama Fig. 4. Astilbe fujisanensis Nakai. Mt. Fuji, Sambanse (B. Hayata, July 1924, TI-lecto). Geographical Variation of Astilbe 423 to be endemic to the Izu islands, i.e. Hachijo-jima serrations (Hara 1939) (Figs. 1e, 7). This biternate Island, Izu-oshima Island, Miyake-jima Island, leaf (Fig. 3h) is also considered to be a kind of Mikura-jima Island, and Kodzu-jima Island (Figs. neoteny as in A. simplicifolia and A. hachijoensis. 1c, 5). The species is well characterized by the Most juvenile leaves of this species are simple thick, lustrous ternate to biternate (in larger ones) (Fig. 3i) as leaves of A. simplicifolia. There is leaves with rough incised double serrations (Fig. also a possibility that the ternate to biternate leaf 3g). The ternate to biternate leaves are also con- is a derived character and this species is possibly sidered to be a kind of neoteny as in A. simplici- a derived one. In Gifu Prefecture, plants with bit- folia. There is also a possibility that the ternate to ernate to triternate leaves (Fig. 3j) were collected. biternate leaves are a derived character and this The ternation of leaves is variable from biternate species is also a derived one. The morphological to triternate. Plants with triternate leaves ap- characters of leaves of this species is similar to proach to A. odontophylla var. odontophylla dis- those of A. simplicifolia and the distribution area tributed in same locality (Fig. 3k). The phyloge- is near to that of A. simplicifolia. Though the phy- netic relationship is not yet clear, but the logenetic relationship in the genus Astilbe is not morphological characters of leaves of this species yet clear, this species seems to be close to the lat- is similar to those of A. odontophylla (var. odon- ter. This species has distinct distribution area not tophylla) and the distribution is a part of the dis- overwrapped with other species including A. tribution range of A. odontophylla (s. str.). This thunbergii and the morphological character of species grows in wet places, such as on wet rocks leaves support its distinctness. or soils by streams. This species is considered to be derived from A.