Island golden saxifrage (Chrysosplenium insularis) in Saxifragaceae from southern islands of South Korea

NEWS - Island golden saxifrage (Chrysosplenium insularis sp. nov.) in the Saxifragaceae from the southern islands of the Republic of Korea is morphologically similar to Chrysosplenium japonicum (Maxim.), differing in that it has fairly persistent bulbils, green to yellowish-green sepals, 4 stamens and cylindrical papillose seeds.

Chrysosplenium L. is a perennial herbaceous member of the Saxifragaceae comprising over 70 species, mostly distributed in temperate regions of the Northern Hemisphere and shaded and moist habitats in mountains. Biogeographically, Chrysosplenium is known to originate from East Asia and several independent lineages have migrated to the New World.

Thirteen species of Chrysosplenium are recognized on the Korean Peninsula (C. flaviflorum, C. epigealum, C. ramosissimum, C. valdepilosum, C. aureobracteatum, C. barbatum, C. ramosum, C. grayanum, C. sinicum, C. macrostemon, C. japonicum, C. serreanum and C. flagelliferum).

During a floristic survey in southern Korea in March 2020, researchers discovered a new species restricted to the southern Korean islands that flowers and fruits from March to May.

Distribution South Korean coastal areas (Jeju-do and Gageo-do Islands). Forests, wet places in forests and shaded places on riverbanks. The specific epithet “insularis” refers to the distribution on the islands. The local name is island golden saxifrage: Seom-gwaeng-i-nun (섬괭이눈).

C. insularis is a perennial herb, hermaphroditic, 5–15 cm tall. Bulbils present near stem base, fairly persistent, pink, turning darkish brown, pilose. Roots fibrous, white. Stems erect, cespitose, light green to green, sparsely hairy, without stolons.

Basal leaves of flowering stems 1–6, opposite, simple, estipulate; petiole 3–9 cm long, glabrescent or sparsely hairy; blade reniform, 13–20 mm × 15–25 mm, apex rounded and often retuse, margins dentate to crenate, 13–17 teeth, base cordate, adaxially green, pilose, abaxially pale green, subglabrous.

Cauline leaves of flowering stems 1–4, alternate, simple, estipulate; petiole 5–22 mm long, glabrescent or sparsely hairy; blade flabellate to reniform, 7–12 mm × 11–18 mm, apex retuse and often rounded or obtuse, margins dentate to crenate, 9–13 teeth, base cordate to broadly cuneate, adaxially green, pilose, abaxially pale green, subglabrous.

Inflorescences terminal, 6–14 flowered cymes, surrounded by leaf-like bracts; peduncles 4.59–18.54 mm long; pedicels 0.5–1.5 mm long, sparsely pilose; bracteal leaves by inflorescence 3, petiole 0.2–4.7 mm long, glabrescent or sparsely hairy; blade subflabellate to orbicular, 2–18 × 2–14 mm, apex truncate and often retuse, margins dentate to crenate, 5–9 teeth, base broadly cuneate to subcordate, adaxially green, sparsely pilose to glabrescent, abaxially pale green, subglabrous.

Flowers 4-merous, actinomorphic; sepals petaloid 4, free, erect to subspreading, ovate to broadly ovate, 1.2–2.1 × 1.5–3.1 mm, apex obtuse or rounded, yellowish green to green, glabrous; stamens 4; filaments narrow conical, 0.3–0.4 mm long; anthers 0.2 mm long, yellow; pistil 2-carpellate, semi-inferior; 1-locular ovary; styles 2, free, erect, 0.2–0.3 mm long; stigma round; disc present.

Capsules 2-lobed, horn-shaped, lobes subequal, 2.8–3.7 × 3.8–5.2 mm long, green, glabrous, dehiscent along the adaxial suture. Seeds numerous, ovoid-ellipsoid, 0.7–0.9 × 0.5–0.6 mm, brown to dark brown, cylindrical papillose on smooth surfaces.

Among the species distributed in Korea, C. insularis is morphologically similar to C. japonicum in terms of leaf arrangement, leaf margins and bractal color. However, clear differences are seen in the bulbil shape (present, fairly persistent vs. present].

Bracteal leaf surface (adaxial sparsely hairy to glabrous, abaxial subglabrous vs. mostly glabrous), sepal color (green to yellowish green vs. yellowish green to yellow), number of stamens (4 vs. usually 8) and seed surface (cylindrical papillose vs. papillose).

The new species is morphologically similar to C. alternifolium distributed in northern Eurasia, differing in stolons (absent vs. present), bract color (green vs. yellow), sepal color (green to yellowish green vs. golden yellow), number of stamens (4 vs. 8) and seed surface (cylindrical papillose vs. smooth).

Original research

Jang JE, Park BK, Lee K-H, Kim H-J, Gil H-Y (2024). Description and phylogenetic position of a new species, Chrysosplenium insularis J.E.Jang, K.H.Lee & H.Y.Gil (Saxifragaceae), from the southern islands of South Korea. PhytoKeys 248: 91-104, DOI:10.3897/phytokeys.248.131291

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