Research Article |
Corresponding author: Bo Li ( hanbolijx@163.com ) Academic editor: Eberhard Fischer
© 2017 Yunhong Tan, Derong Li, Yongjun Chen, Bo Li.
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:
Tan Y, Li D, Chen Y, Li B (2017) Premna bhamoensis (Lamiaceae, Premnoideae), a new species from Kachin State, northeastern Myanmar. PhytoKeys 83: 93-101. https://doi.org/10.3897/phytokeys.83.12869
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In the present study, we describe and illustrate a new species, Premna bhamoensis Y. T. Tan & B. Li (Lamiaceae), from Myanmar. In the 1980s, this species was transplanted from Bhamo County in northeastern Myanmar to the Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences. The species shows striking morphological similarity to P. menglaensis B. Li, and thus, has been misidentified as the latter for a long period of time. However, morphological comparison revealed that P. bhamoensis is distinct from P. menglaensis in many aspects. Moreover, literature survey and specimen examinations also indicated that P. bhamoensis is undoubtedly different from all seven known congenetic species recorded from Kachin State, Myanmar, and a key for their identification has been provided in this paper.
China, morphology, Myanmar, Premna menglaensis , Xishuangbanna Tropical Botanical Garden
The genus Premna L. is one of the largest woody genera belonging to the mint family, consisting of approximately 200 species distributed mainly in the Old World tropics and subtropics (
With 46 species recognized in China, Premna is the fifth largest genus in Lamiaceae flora of China (
Morphological observations of the new species were carried out based on living plants as well as dry specimens, during the period from 2011 to 2016. Measurements were made using a ruler and a micrometer. Both herbarium and fresh specimens of P. menglaensis were examined under a stereo dissecting microscope (StereoZoom® Leica S8 APO, © Leica Microsystems 2017). The conservation status of the new species was evaluated based on the guidelines of the International Union for Conservation of Nature (
The species is most similar in morphology to P. menglaensis B. Li, but differs from the latter in having branchlets and petioles densely tomentose (vs. glabrous or glabrescent), leaf blades papery with minute pubescence (vs. leathery and glabrous), flowers green to greenish yellow (vs. red flowers), calyces slightly 2-lipped with five equal lobes (vs. calyces distinctly 2-lipped with entire or minute emarginate lips), and stamens exserted from corolla (vs. included).
MYANMAR. Kachin State, Bhamo County, voucher from a cultivated plant at the Xishuangbanna Tropical Botanical Garden, Menglun Town, Mengla County, Yunnan Province, Alt. 550 m, 21.404408N, 101.152401E, 10 June 2011, B. Li LB0399 (fruiting branches) (holotype: IBSC!; isotypes: IBSC!, JXAU!, HITBC!).
Woody shrubs, climbing. Branches brown, terete, with an interpetiolar ridge and sparse small yellow elliptic lenticels, sparsely and minutely pubescent to glabrescent. Branchlets grayish to brownish, densely tomentose, without bracts at the base. Leaves simple, opposite-decussate, ovate-oblong to elliptic, papery, 9.0–17 × 4.5–7.5 cm, apex long caudate to caudate-acuminate, base cuneate, subrounded to slightly cordate, margin entire; adaxial surface subglabrous except minutely hirsute on veins; abaxial surface densely pubescent with sparse, yellowish-brown glands; veins 4–8 pairs, abaxially raised and adaxially slightly compressed, secondary veins curved and jointed near margin; petiole 1.5–4.5 cm long, furrowed on upper part, densely yellowish-brown pubescent. Inflorescences terminal, mostly pyramid-shaped thyrse, densely dusty brownish-yellow pubescent, 4.0–7.5 cm long; peduncles 1.5–2.5 cm long; bracts ovate-lanceolate to lanceolate-linear, 0.6–1.2 cm long, easily deciduous; bracteoles linear or lanceolate-linear, 1.0–2.5 mm long; pedicels 0.5–1.5 mm long. Calyx campanulate, 2.5–3.0 mm long, slightly 2-lipped with five equal lobes, apex acute, outside minutely brownish pubescent with brown glands; fruiting calyx distinctly 2-lipped with one lip 2-lobed and another 3-lobed, apex obtuse to subrounded. Corolla green to greenish yellow, 2-lipped, 4.5–5.5 mm long; tube 2.5–3.0 mm long, outside glabrous, inside densely white villose around throat; upper lip 1-lobed, entire, broadly oblong-obovate, obovate, concave, apex subrounded, outside glabrous or slightly pubescent; lower lip 3-lobed, middle lobe rounded to obovate, lateral lobes broadly oblong-ovate or ovate. Stamens 4, didynamous, filaments greenish-white, glabrous, slightly exserted; anther white. Ovary obovoid, 1.0–1.5 mm long, minutely pubescent and golden glandular near the apex; style white, slender, 3.5–4.5 mm long. Fruits drupaceous, purplish dark brown, obovoid to obovoid-ellipsoid, 7.0–8.0 × 4.5–5.5 mm, sparsely dusty pubescent and glandular.
Flower buds were observed in early April. Flowering was observedfrom mid-May to early June and fruiting from late May to late June.
Per the introduction record, P. bhamoensis is originally collected from northeastern Myanmar, but currently known only from the cultivated type in the Xishuangbanna Tropical Botanical Garden (Figure
The specific epithet of this new species, “bhamoensis”, is derived from the name of the locality, Bhamo County, from where the species was originally collected.
Since we have neither rediscovered the wild population of P. bhamoensis in Myanmar, nor identified any other specimens in the herbarium, very few details about its natural distribution and/or population status are currently known. Therefore, the information is inadequate to assess the species’ risk of extinction, whether directly or indirectly. In accordance with the IUCN Red List Categories (
MYANMAR. Kachin State, Bhamo County, voucher from a cultivated plant at the Xishuangbanna Tropical Botanical Garden, Menglun Town, Mengla County, Yunnan Province, Alt. 550 m, 21.404408N, 101.152401E, 31 May 2012, Y. H. Tan 120 [flowering branches] (XTBG!).
Among the seven Premna species recorded in the flora of Kachin State, Myanmar (
Among the Asian Premna, P. menglaensis, as the introduction label indicated, is the species showing the maximum level of similarity to P. bhamoensis. Both are climbing Woody shrubs with ovate-oblong to elliptic leaves, and congested pyramid-shaped inflorescences. However, P. bhamoensis can be easily distinguished from P. menglaensis on the basis of the differences observed in a number of traits, e.g., branchlets and petioles (densely pubescent vs. glabrous or glabrescent), leaf blades (papery and minutely pubescent vs. leathery and glabrous), flower color (green to greenish yellow vs. red), calyx shape (slightly 2-lipped with five equal lobes vs. distinctly 2-lipped with entire or minute emarginate lips), stamens length (exserted from corolla vs. included) (Figure
1 | Inflorescences spikelike | P. interrupta |
– | Inflorescences compound cymes | 2 |
2 | Branchlets, leaves, and petioles covering dense stellate hairs | 3 |
– | Branchlets, leaves, and petioles glabrous or covering other type of hairs | 4 |
3 | Leaf blades ovate to ovate-oblong; cymes in a lax conical panicle | P. tomentosa |
– | Leaf blades elliptic to oblong-lanceolate; cymes in a lax flat-topped corymbs | P. bengalensis |
4 | Vines; branches and leaves glabrous | P. scandens |
– | Trees, erect or climbing Woody shrubs; branches and leaves pubescent | 5 |
5 | Base of branchlets surrounded by bracts | 6 |
– | Base of branchlets without bracts | 7 |
6 | Corymbs ca. 15 cm in diameter, peduncles slender; leaf blades turn brownish black when dry | P. khasiana |
– | Corymbs ca. 4 cm in diameter, peduncles robust; leaf blades brownish yellow when dry | P. barbata |
7 | Leaves margins strongly serrulate; branches without interpetiolar ridges | P. pinguis |
– | Leavesmargins entirely; branches with interpetiolar ridges | P. bhamoensis |
The authors are grateful to the keepers of IBSC, KIB and XTBG for offering kind assistance during specimen examination, and to Dr. Zhonghui Ma and Dr. Zhuqiu Song for their assistance while performing the field surveys. We also thank Zhengmeng Yang for the illustration. This work was supported by the National Natural Science Foundation of China (grant no. 31460044), and the Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences (Y4ZK111B01).