RESEARCH ARTICLE Plant Taxonomy
New distribution records of two rare species of Cynanchum (Apocynaceae) in South Korea:
Cynanchum thesioides (Freyn) K. Schum. and Cynanchum chinense R. Br.
Bo-Mi NAM
1,2, Sungyu YANG
3and Gyu Young CHUNG
1*
1Division of Horticulture & Medicinal Plant, Andong National University, Andong 36729, Korea
2International Biological Material Research Center, Korea Research Institute of Bioscience & Biotechnology, Daejeon 34141, Korea
3Herbal Medicine Resources Research Center, Korea Institute of Oriental Medicine, Naju 58245, Korea (Received 12 December 2019; Revised 10 February 2020; Accepted 12 March 2020)
ABSTRACT: Cynanchum L. in the subfamily Asclepiadoideae (Apocynaceae) includes four recognized species on the Korean peninsula, two of which are native to South Korea. However, the species ranges in South Korea are poorly defined. During a field survey, we discovered C. thesioides, previously unrecorded in South Korea, in Gimpo-si, Gyeonggi-do, and found an additional population of C. chinense, for which only one population has been reported in South Korea. The two taxa are considered rare species with extremely restricted distributions in South Korea, especially C. thesioides. We provide fundamental information, including descriptions, images of the habitats and morphological characters, and a taxonomic key for identification and assessments of the con- servation status of Cynanchum species in Korea.
Keywords: Cynanchum chinense, C. thesioides, new distribution, rare species, unrecorded species
Rare plants typically have narrow distributions and highly specific habitats with limited and/or small populations (I ik, 2011). Many rare plants are vulnerable to habitat loss and/or disturbances by environmental, human, and genetic factors (Lavergne et al., 2005; I ik, 2011). Moreover, the International Union for Conservation of Nature (IUCN) has warned that approximately 13% of plant species in the world are at risk of extinction (Walter and Gillett, 1998). Accordingly, many countries have established a Red List and assessed their threatened species. In Korea, rare plants are mainly organized and protected by the Korea Forest Service and the Ministry of Environment (Korea National Arboretum, 2008; National Institute of Biological Resources, 2012). However, some species, for which little is known about habitat types and population size, are not listed.
Among 15 taxa belonging to Asclepiadoideae in Korea, four in Cynanchum and Marsdenia (C. amplexicaule (Siebold &
Zucc.) Hemsl., C. japonicum (C. Morren & Decne.) Hemsl., C. inamoenum (Maxim.) Loes. ex Gilg & Loes., and M.
tomentosa C. Morren & Decne.) are on the Korean Red List as Endangered and Vulnerable species (Korea National Arboretum, 2008). Despite the highly narrow distributions of Vincetoxicum glabrum (Nakai) Kitag. (= Cynanchum glabrum Nakai) and V. volubile Maxim. (= C. volubile (Maxim.) Hemsl.), they are not included in the list. To establish a conservation management system, accurate identification and comprehensive analyses of habitats, population sizes, and distributions of Korean Asclepiadoideae taxa are critical.
Cynanchum L. is a large genus in the subfamily Asclepiadoideae (Apocynaceae) with approximately 200 species and a wide distribution throughout the world (Liede and Täuber, 2002; Khanum et al., 2016). The genus is morphologically distinguished from Vincetoxicum Wolf. by twining stems, white latex, and mostly heart-shaped leaves; it also exhibits high diversity in floral structures, especially in corona shapes (Khanum et al., 2016; Nam and Chung, 2018).
In the Korean peninsula, Cynanchum was formerly composed of about 10–12 species, and these included sç
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*Author for correspondence: [email protected]
http://e-kjpt.org, © 2020 the Korean Society of Plant Taxonomists. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
2 Bo-Mi NAM et al.
Vincetoxicum species (Lee, 1996; Lee, 2007; Korea National Arboretum, 2017). However, there are now four recognized species based on morphological and phylogenetic studies: C.
chinense R. Br., C. purpureum (Pall.) K. Schum., C. thesioides (Freyn) K. Schum., and C. wilfordii (Maxim.) Hemsl. (Khanum et al., 2016; Nam and Chung, 2018). C. purpureum and C.
thesioides have been reported in North Korea, C. chinense is restricted to South and North Korea, and C. wilfordii is distributed from the seashore to mountain slopes in the Korean peninsula (Lee, 1996; Im, 1999; Chang et al., 2014).
We report new distribution records of two rare species, C.
chinense and C. thesioides, based on a field investigation in South Korea, including the first observation of C. thesioides in the country. The aims of this study are to evaluate the distribution in South Korea of two rare species with careful morphological examination based on the original descriptions and type specimens, and to provide fundamental information for further studies assessing their conservation status.
Taxonomic Treatment
Cynanchum thesioides (Freyn) K. Schum., Nat. Pflanzenfam.
4: 252, 1895; Vincetoxicum thesioides Freyn, Oestrr. Bot. Z. 40:
124, 1890.—TYPE: RUSSIA. Dahuria, Nertschinsk, 1889, Karo, F.K. 145 (syntypes: K, barcode K000872723!; Z, barcode Z-000001810!).
Perennial herbs. Roots long, cylindrical tuberous. Stems erect or upper part twining, ca 25 cm long, branched or not, white latex, densely pubescent. Leaves opposite, rarely 3-whorled, petiole 0.5–
1.8 mm long or subsessile; blades linear to narrowly lanceolate or sometimes oblong, 2.7–4.8 cm long, 2.0–8.0 mm wide, apex acute or rarely rounded, base cordate or truncate, sometimes oblique with colleters at middle part of leaf base, margin entire, ciliolate, midvein elevated abaxially, lateral veins obscure, puberulent on both sides. Inflorescences umbel-like, axillary to terminal; cymules 1–10-flowered, solitary or clustered; peduncles 2.7–4.6 mm long, puberulent; pedicels 1.2–3.8 mm long, puberulent. Flowers calyx tube very short; lobes 5, triangular 2.3–2.8 mm long, puberulent, ciliate, colleters between inside lobes; corollas white-green, glabrous; tube very short; lobes 5, narrowly triangular to oblong, 3.5–4.3 mm long, mostly twisted with one direction; coronas consisting of fused staminal and interstaminal parts at base; lobes 5, laminar, triangular-lanceolate, up to middle of anthers, apex acute; gynostegia sessile; anthers 5, square, with white appendages, triangular-ovate, as long as gynostegia; pollinaria 5; corpusculum ovoid, ca. 200 µm long, ca. 100 µm wide; caudicles ca. 150 µm long, attached to apical pollinia; pollinia pendulous, ellipsoid, ca.
250 µm long, ca. 120 µm wide; style heads conical, 2-divided umbonate. Fruits not seen.
Phenology: Flowering from July to August. Fruiting not observed.
Korean name: Yang-ban-pul (양반풀) (Lee, 1996; Chang et al., 2014; Korea National Arboretum, 2017).
Distribution: Kazakhstan, China, Mongolia, Russia, and Korea (Gyeonggi-do) (Fig. 1).
Habitat and ecology: Grows on semi-shady slopes of rocky mountains (elev. 343 m) along with Acer pictum Thunb. var.
mono (Maxim.) Maxim. ex Franch., Lindera obtusiloba Blume, Quercus mongolica Fisch. ex Ledeb., Fraxinus rhynchophylla Hance, and Securinega suffruticosa (Pall.) Rehder, among others.
Voucher specimen: KOREA. Gyeonggi-do: Gimpo-si, Wolgot-myeon, Munsusan Mt., 17 Aug 2019, B.-M. Nam &
S. Y. Yang 190817-001 (ANH).
Note: Cynanchum thesioides mainly grows in open disturbed areas, sand dunes, grasslands, and roadsides of Kazakhstan, western China, central and Far East of Russia, Fig. 1. Distribution map based on voucher specimens of Cynanchum thesioides and Cynanchum chinense in South Korea.
★, Cynanchum thesioides; ●, Cynanchum chinense.
Fig. 2. Photographs of Cynanchum thesioides in South Korea. A. Habit. B. Habitat (Gimpo-si, Gyeonggi-do). C. Root. D. Stem with latex. E.
Petiole. F. Leaf. G. Inflorescence. H. Flower (one corolla lobe removed). I, J. Corona and gynostegium (side and front views). K. Pollinarium.
4 Bo-Mi NAM et al.
Mongolia, and North Korea (Hwanghae-do and Pyeongannam-do) (Li et al., 1995; Lee, 1996; Im, 1999;
Chang et al., 2014). It is morphologically characterized by linear to narrowly lanceolate leaves, mostly puberulent; an erect stem with twining apical parts; triangular-lanceolate corona lobes; and broadly fusiform follicles (Li et al., 1995) (Fig. 2). During the field survey, we discovered the first population of C. thesioides in Gimpo-si, Gyeonggi-do, South Korea, very close to North Korea (Figs. 1, 3A, B).
The population only included 18 individuals along with Acer pictum Thunb. var. mono (Maxim.) Maxim. ex Franch., Lindera obtusiloba Blume, Quercus mongolica Fisch. ex
Ledeb., Fraxinus rhynchophylla Hance, and Securinega suffruticosa (Pall.) Rehder. Two individuals flowered, and fruit set was not observed. We believe that this is the only population in South Korea and that the species is dependent mainly on asexual reproduction. The species can be categorized as critically endangered (CR) based on the B2 criterion of IUCN (IUCN Standards and Petitions Committee, 2019) because its area of occupancy in South Korea is smaller than 10 km2. However, to assess the conservation status, an intensive investigation is required, including analyses of population/individual sizes with careful taxonomic revision.
Fig. 3. Photographs of habitats of Cynanchum thesioides and Cynanchum chinense in South Korea. A, B. Habitat of C. thesioides (Gimpo-si, Gyeonggi-do). C, D. Habitat of C. chinense (Hwaseong-si, Gyeonggi-do).
Fig. 4. Photographs of Cynanchum chinense in South Korea. A. Habitat (Hwaseong-si, Gyeonggi-do). B. Root. C. Stem with latex. D. Leaf. E.
Inflorescence. F. Flower and calyx. G. Flower. H. Corona (partly removed) and gynostegium. I. Corona with appendages. J. Pollinarium. K.
Gynoecium. L. Fruit. M. Seed with coma.
6 Bo-Mi NAM et al.
Cynanchum chinense R. Br., Mem. Wern. Nat. Hist. Soc.
1: 44, 1810.—TYPE: CHINA. Provincia Pechiley, Georgius Staunton, Baronettus, Staunton s.n. (holotype: BM, barcode BM001014201!).
C. pubescens Bunge, Enum. Pl. China Bor. 44, 1831;
Vincetoxicum pubescens (Bunge) Kuntze, Revis. Gen. Pl. 2:
423, 1891.
C. deltoideum Hance, Ann. Sci. Nat., Bot., sér. 5: 228, 1866.
Perennial herbs. Roots long, cylindrical tuberous. Stems twining, many branched, terete, pubescent, white latex.
Leaves opposite, petiole 22.6–41.0 mm long, 1.0–1.6 mm wide; blades triangular or triangular-ovate, 1.6–7.9 cm long, 3.1–7.1 cm wide, apex acute or acuminate, base rounded or cordate rarely truncate, 4–7 colleters at base, margin entire, ciliolate, lateral veins 5–9 pairs, pubescent usually on veins. Inflorescences axillary to terminal, dichasial cyme, 2 to 32-flowered, usually branched at base, 11.7–73.4 mm long; peduncles 1.2–29.2 mm long, 0.4–
1.2 mm wide, pubescent; pedicels 1.5–6.0 mm long, 0.2–
0.6 mm wide, pubescent; bracts lanceolate, 0.8–1.9 mm long, 0.1–1.1 mm wide. Flowers calyx longer than corolla tube; tube short; lobes 5, lanceolate, apex acute, pubescent, 1–2 colleters between inside lobes; corollas white; lobes 5, linear-lanceolate, rounded, recurved, glabrous; coronas white; tubular, laminar, as long as gynostegium; lobes 5, fused with tube inside, apex linear, longer than gynostegium, usually recurved; corona appendages threadlike on lobes inside, shorter than lobes; gynostegia sessile; anthers 5, triangular-ovate, appendages exceeding gynostegium; lateral 2 anther wings projected on base;
anther wings parallel to each other; pollinaria 5;
corpusculum ellipsoid, 163–300 µm long, 100–133 µm wide; caudicles 60–70 µm long, attached to apical pollinium; pollinia pendulous, ellipsoid, 233–333 µm long, 100–167 µm wide; style heads conical, 2-divided umbonate. Fruit follicles, usually one per flower, linear, 84.0–129.8 mm long, 4.6–7.5 mm wide, pubescent. Seeds 36–64 per follicle, oblong, 4.3–6.9 mm long, 1.8–3.1 mm wide, winged, brown, glabrous; comas 17.7–40.6 mm long.
Phenology: Flowering in August, fruiting from September to October.
Korean name: Ga-neun-teol-baek-mi (가는털백미) (Chang et al., 2014; Korea National Arboretum, 2017).
Distribution: China, Mongolia, and Korea (Incheon and Gyeonggi-do) (Fig. 1).
Habitat and ecology: In Korea, the species grows in open areas of seashore, swamp edges, and roadsides, along with
Carex sp. (dominant species), Phragmites australis (Cav.) Trin.
ex Steud., Artemisia lancea Vaniot, Conyza canadensis (L.) Cronquist, etc.
Voucher specimens: KOREA. Gyeonggi-do: Hwaseong-si, Namyang-eup, Munho-ri, 17 Aug 2019, B.-M. Nam & S. Y.
Yang 190817-002–005 (KIOM). Incheon: Ganghwa-gun, Samsan-myeon, Seongmodo Isl., 2 Sep 2014, B.-M. Nam &
G.Y. Chung 140902-100–109 (ANH); 9 Aug 2016, B.-M. Nam
& G.Y. Chung 160809-100–103 (ANH).
Note: Cynachum chinense mainly occurs in thickets, roadsides, seashores, and riverbanks in China, Mongolia, and Korea (Li et al., 1995). It is clearly distinguished from other species within the genus Cynanchum by its triangular leaves with cordate bases and a tubular corona with long and slender appendages (Nam and Chung, 2018) (Fig. 4). Previously, the species has only been observed on the seashore and saltern areas of Is. Seokmodo, Incheon, South Korea. We found an additional natural population in the inland area of Hwaseong- si, Gyeonggi-do (Figs. 1, 3C, D). C. chinense is considered a rare species, found in only two locations in South Korea;
however, no attempts have been made to assess its conservation status to date. To determine the correct IUCN category, more data for population size and demographic changes are needed.
Key to the genus Cynanchum in South Korea
1. Stems erect, apically twining; leaf blades linear to narrowly lanceolate ··· C. thesioides (양반풀) 1. Stems twining, leaf blades triangular to ovate
2. Leaf basal lobes incurved; inflorescences dichasium;
corolla lobes white; coronas tubular; follicles linear ···
··· C. chinense (가는털백미) 2. Leaf basal lobes not incurved; inflorescences umbellate cyme; corolla lobes yellow-green; coronas deeply lobed; follicles fusiform ··· C. wilfordii (큰조롱)
ORCID: Bo-Mi NAM: https://orcid.org/0000-0002-6769-9317;
Sungyu YANG: https://orcid.org/0000-0001-5081-0296; Gyu Young CHUNG: https://orcid.org/0000-0002-4891-1140
Acknowledgments
The authors deeply thank to Mr. C. J. Lee for providing the information on the habitat of C. thesioides. This research was supported by a grant (18172MFDS201) from the Ministry of Food and Drug Safety in 2019.
Conflict of Interest
The authors declare that there are no conflicts of interest.
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