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Korean J. Pl. Taxon > Volume 53(1); 2023 > Article
AIYAKOOL and VAJRODAYA: Glycosmis kanburiensis: A new species of Rutaceae from Thailand


Glycosmis kanburiensis (Rutaceae) from Kanchanaburi Province, southwestern Thailand is described as a new species. It is similar to G. esquirolii (H. Lév.) Tanaka in its dendriform habit, terminal inflorescences, and large leaflets, but several easily recognizable differences in floral features, including triangular sepals with rust-colored indumentum (vs. broadly ovate villose sepals), globose, glabrous (vs. subglobose, villosus) ovary, cylindrical and attenuate (vs. stout) style, and ellipsoid (vs. globose) fruit. A taxonomic description, illustration, photographs, geographical distribution, ecological data, and conservation status are provided.


The most distinguishing characteristics that separate Glycosmis (Rutaceae; Aurantioideae; Clauseneae [Kubitzki et al. 2011]) from related genera are its unarmed nature and the rust-colored villosulose indumentum covering young twigs, buds and inflorescences (Swingle and Reece, 1967; Stone, 1985; Jones, 1995; Zhang et al., 2008; Kubitzki et al., 2011). Glycosmis comprises about 52 species mainly distributed in tropical and subtropical Asia and Australia (Zhang et al., 2008; Kubitzki et al., 2011; POWO, 2022). In Thailand, 13 species and two varieties of Glycosmis were reported by Craib (1934), Guillaumin (1946), Stone (1985), and Pooma and Suddee (2014). Three species: G. parva Craib, G. puberula Lindl. ex Oliv. var. subsessilis (Craib) B. C. Stone and G. suberosa H. Toyama & Rueangr. are endemic to Thailand. Five species, including G. chlorosperma (Blume) Spreng. (10–12 m), G. craibii Tanaka (5 m), G. esquirolii (H. Lév.) Tanaka (6–10 m), G. macrophylla (Blume) Miq. (8–10 m), and G. pentaphylla (Retz.) DC. (5 m), have a predominantly dendriform habit (Craib, 1934; Stone, 1978, 1985, 1994; Toyama et al., 2016; POWO, 2022).
During a botanical excursion in Kanchanaburi Province, we encountered a predominant arborescent species of Glycosmis with large leaflets. After we compared the plants with description of the literature (Hooker, 1875; Kurz, 1877; Guillaumin, 1911; Craib, 1934; Stone, 1985; Jones, 1995; Zhang et al., 2008; Pooma and Suddee, 2014; Toyama et al., 2016) and with specimens in herbaria, we were unable to match these plants with any of the known species in the genus. We therefore describe these plants as a new name Glycosmis kanburiensis W. Aiyakool & S. Vajrodaya.


Field excursions were undertaken in March 2017 and February 2018 in Sangklaburi District, Kanchanaburi Province. Specimens were collected using standard procedures for herbarium specimens (Bridson and Forman, 1999). The specimens were mounted on herbarium sheets and deposited in the Bangkok Herbarium (BK) and the Suan Luang Rama IX Royal Botanic Garden (SLR), Thailand.
Morphological characters of vegetative and reproductive parts were examined both in the field and on herbarium specimens. Plant parts were dissected and investigated through use of a stereomicroscope. Photographs of the plants parts were taken and illustrations were made. The morphological comparisons were made using relevant literature (Hooker, 1875; Kurz, 1877; Guillaumin, 1911; Craib, 1934; Stone, 1978, 1985, 1994; Jones, 1995; Zhang et al., 2008; Toyama et al., 2016). The morphology of herbarium collections of closely related species was examined in specimens in BK, BKF, CMU, CMUB, KKU, PSU, QBG, and SING and in high-resolution images of specimen available on the websites of the Kew Herbarium Catalogue (http://apps.kew.org/herbcat/navigator.do), Natural History Museum, London (https://www.nhm.ac.uk/research-curation/scientific-resources/collections/botanical-collections), and the Muséum National d’Histoire Naturelle, Paris (https://science.mnhn.fr/institution/mnhn/collection/). The conservation status was assessed following the criteria given by the IUCN (2019).


Glycosmis kanburiensis W. Aiyakool & S. Vajrodaya, sp. nov.––THAILAND. Kanchanaburi Province: Sangkhla Buri District, Prangphle, 14°58′48.0″N, 98°38′07.3″E, 22 Mar 2017, W. Aiyakool, S. Vajrodaya, N. Wongthet, W. Muangrom, & K. Thaweepanyaporn 179 (holotype: BK [BK No. 082574], isotype: BK, SLR) (Figs. 1, 2).
Diagnosis: Glycosmis kanburiensis is most similar in morphology to G. esquirolii but differs in having triangular sepals covered with rust-colored indumentum (vs. broadly ovate villose sepals), ovary globose and glabrous (vs. subglobose and villose), style cylindrical and attenuate (vs. stout) and fruit ellipsoid (vs. globose).
Trees, evergreen, unarmed, 10–15 m tall, Diameter at breast height (DBH) 1–35 cm. Bark smooth, grayish brown; inner bark white; young branches densely covered with caducous rust-colored indumentum; old branches terete, almost glabrous, whitish brown or grayish brown. Leaves alternate, pinnately compound, 28–42 × 17–35 cm ; petiole 4.5–8 cm long; leaflets 3–9, mostly 5-foliolate, densely covered with caducous rust-colored indumentum when young, glabrous at maturity; petiolules 0.8–1.2 cm long; leaflet blades ovate-lanceolate to elliptic, 18–22 × 8–12 cm, subcoriaceous, abaxial surface grayish-green, adaxial surface dark green, lustrous, base cuneate, margin entire, recurved, apex acuminate or acute-obtuse, pellucid gland-dotted; midrib, prominent abaxially, sunken or almost flat adaxially; secondary veins 7–9 pairs, brochidodromous, faintly prominent adaxially, finely reticulate abaxially; tertiary veins faintly visible on both surfaces. Inflorescences terminal, paniculate, 20–35 cm long, of 3–5 racemes, with many densely arranged flowers; peduncle 4–10 cm long; bracts absent; pedicels absent or to 0.3 cm long, densely covered with rust-colored indumentum. Flowers bisexual, pentamerous; sepals triangular, 2–2.2 × 1.2–1.5 mm, brown, coriaceous, outer surface with rust-colored indumentum, inner surfaces glabrous; petals ovate-elliptic, 8–10 × 2–4 mm, pale yellow or white, subcoriaceous, outer surface with rust colored indumentum, inner surface glabrous, margin entire, apex acute to obtuse, reflexed at anthesis; stamens 10, in two whorls of 5, incurved, stamens in outer whorl antipetalous, longer, 4.5–5.5 mm long, those in inner whorl antisepalous, shorter, 3–4 mm long; filaments of outer whorl longer, 3–3.5 mm long, those of inner whorl shorter, 1.5–1.8 mm long; anthers dorsifixed, 1.8–2 × 0.8–1.2 mm, glabrous, longitudinally dehiscent; disk annular; gynophore 0.2–0.4 cm long, swollen near joint with ovary, glabrous; ovary globose, 5-locular, glabrous, 3.8–4 × 3.5–4.5 mm; style cylindrical, attenuate, 1.5–1.8 mm long, persistent; stigma capitate, ca 0.1 cm long. Fruit berries, oblong-ellipsoid, 3.5–4.8 × 2.8–3.7 cm, greenish, becoming yellowish when ripe, glabrous; seeds 1 or 2, globose-ellipsoid, 2.2–2.8 x 2.0–2.2 cm.
Additional specimen examined: THAILAND. Kanchanaburi: Sangkhla Buri district, Ban Pompi, in bamboo forest, 28 Mar 1967, Prayad Sangkhlachand 724 (BK); ibid, in mixed deciduous forest, 1 Apr 1967, B. Nimanong 12 (BKF).
Phenology: Flowering January to March, fruiting March to May.
Etymology: the specific epithet refers to Kanburi which is a dialectal name of Kanchanaburi Province.
Vernacular name: Khoei Tai Mueang Khan, the name given by us.
Distribution, ecology, and conservation status: Glycosmis kanburiensis is endemic to southwestern Thailand and known only near the type locality in Prangphle and Pompi, Sangkhlaburi District, Kanchanaburi Province (Fig. 3). It is usually scattered in areas with moist substrate near streams or at the base of limestone hills in dry evergreen forests and mixed deciduous forests at 265–400 msl. The major associated species of trees are Dipterocarpus baudii Korth., Swintonia floribunda Griff., Murraya paniculata (L.) Jack., Arenga pinnata (Wurmb) Merr. and Bambusa spp. Glycosmis kanburiensis is preliminarily assessed as Endangered (B1ab(ii), B2ab(ii)) following the criteria of the IUCN (2019). From the known localities in Kanchanaburi Province, the Extent of Occurrence (EOO) is less than 150 km2 and the Area of Occupancy (AOO) is about 12 km2 at two localities where it is restricted to fragmented small populations of around 10 mature individuals each. They are not within protected areas and may be destroyed by agricultural activities, human disturbance, and tourism.
Note: Glycosmis kanburiensis, our proposed new species from southwestern Thailand, is similar to Glycosmis esquirolii (H. Lév.) Tanaka, of China, Myanmar, and northern Thailand (Appendix 1) in its dendriform habit, large leaflets, and inflorescences seemingly terminal, but differs in having relatively smaller reproductive parts, triangular sepals covered with rust-colored indumentum (vs broadly ovate, villose sepals), petals obovate-elliptic, 8–10 × 2–4 mm and covered with rust-colored indumentum (vs. petals oblong-lanceolate, 4.5–5.5 × 2.5–3 mm and villose), ovary globose, 3.8–4 × 3.5–4 mm and glabrous (vs. ovary subglobose, 1–1.5 × 0.8–1.2 mm long) and villose, style cylindrical, attenuate, 1.5–1.8 mm long (vs. stout, 0.5–1 mm long) and fruit ellipsoid and 3.5–4.8 cm long (vs. globose and 1.5–2.8 cm long) at maturity (Figs. 3, 4).
Glycosmis kanburiensis also resembles G. chlorosperma (Blume) Spreng., G. craibii Tanaka, G. macrophylla (Blume) Miq., and G. pentaphylla (Retz.) DC. However, G. chlorosperma, G. macrophylla and G. pentaphylla have axillary inflorescence, and G. craibii has much smaller subglobose fruit (Table 1). The distinguishing characteristics of G. kanburiensis and related species in Thailand are provided in Table 1.


We thank Professor Uamporn Veesommai, who first found Glycosmis kanburiensis and who provided valuable information and suggestions, and the curators and staff of BK, BKF, CMU, CMUB, KKU, PSU, QBG and SING for their support and access to the specimen collections. Thanks are also due to members of the Comparative and Ecological Phytochemistry lab for their assistance during the field trips. We also want to thank the administrators of the Science Achievement Scholarship Fund of Thailand (SAST) for their funding.


The authors declare that there are no conflicts of interest.

Fig. 1.
Illustrations of Glycosmis kanburiensis A. Flowering branch. B. Flower. C. Androecium. D. Petal. E. Pistil. F. Antisepalous stamen. Illustration by W. Aiyakool.
Fig. 2.
Photographs of Glycosmis kanburiensis. A. Habit. B. Flowering branch. C. Bark of stem. D. Young terminal bud. E. Flower and immature fruit. F. Flower. G. Pistil. H. Androecium. I. Antisepalous stamen. J. Petal. K. Fruit. Photo AD and FK by W. Aiyakool, E by U. Veesommai.
Fig. 3.
Distribution of Glycosmis kanburiensis. in southwestern Thailand (yellow dot) and Glycosmis esquirolii in northern Thailand (red dot).
Fig. 4.
Morphology of inflorescence branch (A, E), pistil (B, F), petal (C, G), and fruit (D, H) of Glycosmis kanburiensis and G. esquirolii (H. Lév.) Tanaka. AD. G. kanburiensis. EH. G. esquirolii. Photo AD, F, and G by W. Aiyakool, E and H by K. Khammongkol.
Table 1.
Morphological comparison between Glycosmis kanburiensis and the related species.
Characters G. kanburiensis G. chlorosperma G. craibii G. esquirolii G. macrophylla G. pentaphylla
Habit Small tree, 12–15 m tall Shrub to small tree, 0.8–10 m tall Shrub to small tree, 0.5–5 m tall Small tree, 3.5–12 m tall Shrub to small tree, 0.5–8 m tall Shrub to small tree, 0.5–2 m tall
Leaves 5–9-Foliolate; leaflet blade obovate to elliptic, margin entire 3–5(7)-Foliolate; leaflet ovate to oblong-lanceolate, margin entire 3–5-Foliolate; leaflet blade oblong-lanceolate ovate, margin entire 5–11-Foliolate; leaflet blade oblong, olong-elliptic, margin serrate or undulate (3)5–9-Foliolate; leaflet blade oblanceolate or elliptic, margin entire 3–5(7)-Foliolate; leaflet blade ovate-lanceolate or long elliptic, margin serrate or undulate
Inflorescence Terminal, 20–35 cm long Pseudo-terminal, 2.5–15 cm long Axillary or terminal, 1.5–3 cm long Terminal, 12–20 cm long Axillary, 1.5–7.5 cm long Axillary, 2–15 cm long
Sepals Triangular, 1.5–2.2 mm long, rust-colored indumentum Ovate, 1.5–2 mm long, rust- colored indumentum Broadly ovate, ca. 1 mm long, pubescent Broadly ovate, 1–1.5 mm long, villosus Broadly ovate, ca. 0.5 mm long, villosus Broadly ovate, ca. 1 mm long, pubescent
Petals Obovate-elliptic, 8–10 mm long, rust-colored indumentum Obovate-oblong, 2–6 mm long, rust-colored indumentum Elliptic, 2–2.5 mm long, pubescent on upper part Oblong-lanceolate, 4.5–5.5 mm long, villosus and glabrous near margin Oblong-elliptic, 2.5–7.5 mm long, villosus Ovate, 5–8 mm, glabrous
Gynoecium Globose, 5-locular, glabrous Pyriform, (4)–5-locular, glabrous Terete or ovate, 5-locular, glabrous Terete, 5-locular, villosus Oblong-ovate, 3-locular, villosus Globose to ovoid, 5-locular, glabrous
Fruit Ellipsoid, 3.5–4.8 cm long Globose, 1–1.25 cm in diam. Subglobose, 0.8–1.4 cm in diam. Globose, 1.5–2.8 cm in diam. Ellipsoid, 1.5–2.5 cm in diam. Globose, 0.5–1.2 cm in diam.
Distribution Thailand SE Asia S. China, N. Thailand, Vietnam Myanmar, S. China, N. Thailand SE Asia, Papua New Guinea, Australia S & SE Asia


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Appendix 1.

Specimens of Glycosmis esquirolii examined in this study

CHINA. Kwei Chou [Guizhou]: J. H. Esquirol 744 (holotype: K (K000382466) seen on digital image).
THAILAND. Chiang Mai: Chiang Dao, 6 Apr 1921, A. F. G. Kerr 5238 (BK). Lampang: Wang Nua, Jae Sawn Nat. Park, 2 Jun 1996, J. F. Maxwell 96-786 (CMUB, BKF). Mae Ta, 13 Feb 1921, A. F. G. Kerr 4841 (BK); Doi Khun Tan, 12 Apr 2017, W. Aiyakool 2017-198 (SLR). Sukhothai: Sri Satchanalai Nat. Park, 16 Nov 2015, C. Marknoi 8358 (QBG); ibid, 17 Nov 2015, C. Marknoi 8398 (QBG); ibid, 4 Feb 2015, C. Marknoi 7339 (QBG).
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