Research Article |
Corresponding author: Ami Oh ( ohamiohami@gmail.com ) Academic editor: Doug Soltis
© 2020 Ami Oh, Sea-Hee Han, Byoung-Un Oh.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Oh A, Han S-H, Oh B-U (2020) Astilbe uljinensis (Saxifragaceae), a new species from South Korea. PhytoKeys 161: 89-98. https://doi.org/10.3897/phytokeys.161.53019
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A new species Astilbe uljinensis B.U.Oh & H.J.Choi is described from Gangwon-do and Kyeongsangbuk-do in South Korea based on its morphological characteristics and distributional pattern. A. uljinensis is easily distinguished not only from three other Astilbe species in South Korea, but all other species in the genus by possessing a green young rachis, dense long whitish glandular hairs on the young rachis, dense long brownish glandular hairs on the mature inflorescence, and a slightly undulated margin of leaf epidermal cells. Specific comparisons of morphological features such as the type of the trichome, the shape of the leaf epidermis cell, and the color of the young rachis that differentiate A. uljinensis from Astilbe chinensis, another South Korean Astilbe species, are provided.
Gangwon-do, Gyeongsangbuk-do, South Korean endemic, morphology, taxonomy, trichome
Astilbe Buchanan-Hamilton. & D. Don (Saxifragaceae, Saxifragales) is composed of approximately 18 species which are distributed in eastern and southern Asia, and eastern North America (
Owing to the large morphological variations in Astilbe, the taxonomy of South Korean Astilbe has remained incomplete to date (
In this study, we report a previously undescribed species whose morphology is clearly distinct from all other species of Astilbe. This undescribed species is restricted to Kyeongsangbuk-do (Uljin-gun) and Gangwon-do (Gangneung-si, Pyeongchang-gun, Samcheok-si), the central regions of South Korea, particularly on the eastern and southern sides of the Baekdudaegan mountain ranges near the eastern coast. Based on morphological and distributional characteristics, this species is identified and described as a novel species from South Korea.
For species description, the type materials in the herbarium of Chungbuk National University (
A comparison with a related taxon was made against Astilbe chinensis, one of the South Korean Astilbe species that is morphologically most similar to the newly described species. A. chinensis is distributed in the East Asian countries of South Korea, China, Russia and Japan (
The morphological observations throughout this study were performed using Zoom 2000 (Leica, Germany), a stereoscopic microscope, ECLIPSE E600 (Nikon, Japan), a light microscope, and JSM-700F (Jeol, Japan), a scanning electron microscope. The brownish glandular hairs on the inflorescence and the whitish glandular hairs on the young shoots were observed using the stereoscopic microscope, and the epidermal cells and the stomatal apparatus were observed using the light microscope and the scanning electron microscope.
This new species is similar to A. chinensis, but differs from it due to the presence of a green young rachis of rhizomatous leaf, dense whitish long glandular hairs and sparse brownish long non-glandular hairs on the young rachis, dense brownish long glandular hairs of 1.5 to 2.7 mm length on the mature inflorescence, ovate-elliptic terminal leaflet, weakly undulated margin of leaf adaxial epidermal cell, and a stomatal apparatus of larger size and lower density on the leaf abaxial epidermis. These differences between A. uljinensis and A. chinensis have been summarized in Table
Morphological differences between Astilbe uljinensis and Astilbe chinensis.
Characters | Character state | A. uljinensis | A. chinensis | |
---|---|---|---|---|
Young rachis of rhizomatous leaf | ||||
Surface | color | always green | reddish to greenish brown | |
glandular hair | type | long hair | dense/whitish | sparse/whitish |
short hair | Absent | sparse/whitish | ||
length (mm) | 0.6–1.0 | less than 0.1 or 0.6–1.0 | ||
non-glandular hair | type | long hair | sparse/brownish | dense/whitish |
Mature inflorescence | ||||
glandular hair | type | long hair | dense/brownish | slightly dense/brownish |
short hair | Absent | slightly dense/brownish | ||
length (mm) | 1.5–2.7 | less than 0.2 or 1.0–2.2 | ||
Leaf | ||||
terminal leaflet | shape | ovate-elliptic | rhomboid-elliptic | |
stomatal apparatus | length (µm) | 23–26 | 20–24 | |
width (µm) | 17–20 | 15–18 | ||
density (no./1mm2) | 28–51 | 51–66 | ||
adaxial epidermal cell | margin shape | weakly undulated | violently undulated | |
Florescence | late Jun. to early Aug. | late Jun. to early Sep. |
South Korea. Gyeongsangbuk-do: Uljin-gun, Sangdanggyo bridge, sunny or shady forest in mountainous area, 110m, 37°03'28.4"N, 129°17'41.6"E, 16 July 2015, B.U.Oh et al., 150716-1 (holotype:
Perennial, 57.4–125.7 cm tall. Roots fibrous, simple and stout, dark brown, 4.4–17.4 cm long, 0.2–0.4 mm in diam. Rhizomes extend, dark brown, 1.8–10.7 cm long, 12.6–26.8 mm in diam. Young shoots with dense long whitish glandular hair and sparse long brownish non-glandular hair on the surface, always green, 2.1–2.5 mm in diam. Rhizomatous leaves 2–3 ternate compound, 3–8 growing from rhizome, 31.5–68.5 cm long, 16.7–26.2 cm wide; terminal leaflet ovate to elliptic, apex acute to acuminate, base rounded or cuneate, margin double serrate, green; blade 52.2–81.3 mm long, 22.4–47.7 mm wide; rachis with dense long glandular hair. Bracts ternate leaf or 2–3 ternate compound, 0–2 growing from the rachis, usually smaller than rhizomatous leaves, 6.4–27.7 cm long, 3.6–13.7 cm wide. Inflorescence raches below bract erect, with dense glandular hair, green to reddish brown, 29.0–91.9 cm long, 2.3–4.7 mm in diam; those above bract developing panicle, 12.3–34.2 cm long, 0.8–2.2 mm in diam, with dense long brown glandular hair; peduncle, 32–40 from rachis, 2.2–7.4 cm long, 0.3–0.8 cm wide; pedicel 0.2–0.6 mm long. Flowers dense on peduncle, purplish red, 6.4–7.7 mm long, 1.4–2.2 mm wide; sepal 5, ovate, apex rounded, margin with short glandular hair, surface glabrous, white, 1.2–1.9 mm long, 0.8–1.0 mm wide; petal 5, linear, 1–veined, apex acute, 6.1–7.4 mm long, 0.2–0.3 mm wide; stamen 10, 3.2–3.9 mm long; filament linear, 2.8–3.4 mm long; anther ellipsoid, bright yellow to purple, 0.4–0.5 mm long; carpel 2, ovoid, surface glabrous, 2.0–2.3 mm long, 1.0–1.4 mm in diam. Fruits capsule, 2-parted, ovoid, green, surface glabrous, 3.3–3.8 mm long, 1.4–1.5 mm wide. Seeds numerous, irregularly ellipsoidal, dark brown, 1.0–1.4 mm long, 0.3–0.4 mm wide.
Currently, A. uljinensis is observed only in the central regions of South Korea, including Gangwon-do (Pyeongchang-gun, Samcheok-si, Gangneung-si) and Gyeongsangbuk-do (Uljin-gun). The species is found either in shady forests or on slopes near streams.
Flowering occurred between early June and late August. Fruiting occurred between July and October.
At present, the known habitats of this new species are not being protected legally. In addition, since this species generally grows near streams, it is vulnerable to flooding. Previously, up to 10–20 individuals were found by the authors in some of this species’ populations. During the course of the present study, only a very small number of individuals were observed in some of the known habitats, probably indicating a decline in the plant population. However, the conservation status for the known populations has not been thoroughly investigated to date. Therefore, in accordance with the
South Korea. Gangwon-do: Pyeongchang-gun Odaesan, 4 July 1989, B.H.Choi, 4090 (
In the present study, the morphology of the trichomes on the plant body was studied extensively (Table
Shapes of trichomes on Astilbe uljinensis and Astilbe chinensis A, B, E, G A. uljinensis C, D, F A. chinensis. Abbreviations. BLN, Brownish Long Non-Glandular Hairs; WLN, Whitish Long Non-Glandular Hairs; WL, Whitish Long Glandular Hairs; WS, Whitish Short Glandular Hairs; BL, Brownish Long Glandular Hairs; BS, Brownish Short Glandular Hairs.
The shape of the leaf epidermal cells was also distinct in this undescribed plant. The adaxial epidermal cells of the new species had weakly undulated margins, while those of A. chinensis had violently undulated margins (Fig.
The present study revealed that the morphology of the trichomes on the plant body, and their density, could be important characteristics for the identification of the newly described species, at the genus level. In addition, the geographical distribution of the undescribed plant is restricted to the central regions of South Korea, Gangwon-do and Gyeongsangbuk-do, which is also distinct compared to the distribution of other Astilbe species. From both the morphological observation and the recognized distribution patterns, we conclude that the previously undescribed plant should be treated as a new species. In this new species, both the macro-morphological and the micro-morphological characteristics are potentially important taxonomic keys for its identification.
This work was supported by a grant from the National Institute of Biological Resources (NIBR), funded by the Ministry of Environment (MOE) of the Republic of South Korea (NIBR202007103).