Premna caridantha Y.H.Tan & Bo Li, 2021

Tan, Yun-Hong, Min, Dao-Zhang, Ding, Hong-Bo, Yang, Bin, Maw, Mya Bhone & Li, Bo, 2021, Premna caridantha (Lamiaceae: Permnoideae), a distinct new species from Kachin State, northern Myanmar, Phytotaxa 490 (1), pp. 107-113 : 108-110

publication ID	https://doi.org/ 10.11646/phytotaxa.490.1.10
persistent identifier	https://treatment.plazi.org/id/21298842-FFA8-346B-14CD-D9F23176F7EB
treatment provided by	Marcus
scientific name	Premna caridantha Y.H.Tan & Bo Li
status	sp. nov.

Treatment

Premna caridantha Y.H.Tan & Bo Li View in CoL , sp. nov., Figs. 1−2 View FIGURE 1 View FIGURE 2

Type:— MYANMAR. Kachin State, Putao District, Nawngmun Township , from Kawlei to Shinsanku , 27°41′14.11″N, 97°53′12.99″E, 1400 m elev., 10 June 2018, Y. H GoogleMaps . Tanet al. M4286 (holotype HITBC-0035004!, isotypes HITBC-0035005!, CSH-0181311!, RAF!) .

Diagnosis: — Premna caridantha is most similar to P. grandipaniculata in having large and intricate paniculiform inflorescences which branch three times with the terminal branch formed by a spike-like thyrse, but clearly differs from the latter in leaf shape (oblong to ovate with acuminate to acute apex vs. broadly ovate to subrounded with sharply acute apex), corolla shape (distinctly 2-lipped with a short incurved tube and a bright yellowish spot on the middle lobe of the lower lip vs. slightly 2-lipped to nearly actinomorphic, straight corolla tube and without a yellowish spot), and stamen orientation (exerted under the upper lip vs. nearly radially exerted).

Description: —Woody climber. Branches brown, terete, spreading, covered by dense white elliptic lenticels, tomentose, with an interpetiolar ridge between petioles; branchlets dark green, glabrous, base surrounded by small bracts. Leaves simple, opposite-decussate, usually unequal in size, glabrous, oblong to ovate, leathery, 9.3–18.8 × 7.6–11.5 cm, apex acuminate to acute, base cuneate to broadly cuneate, margin entire; veins 6–10 pairs, abaxially raised and adaxially slightly compressed, secondary veins curved and jointed near margin; petiole 0.4–1.8 cm long, slightly inflated. Inflorescences terminal, large and paniculiform branching three times, 16–23 cm long, 9–15 cm wide, peduncle minutely puberulous but nearly glabrous when mature, terminal branches spike-like thyrses, minutely brownish pubescent, 5–7.5 cm long, formed by sessile cymes laxly arranged on the axis; bracts ovate, 3–10 mm long, easily deciduous; bracteoles subulate, tiny. Calyx campanulate, 2–2.5 mm long, outside minutely brownish pubescent, strongly 2-lipped, both lips entire with obtuse apex. Corolla yellowish white, sub-glabrous, 2.5–3.5 mm long, 2-lipped, tube incurved, inside densely white villose around the throat; upper lip straight, deeply emarginate; lower lip 3-lobed, lobes subequal, obovate, strongly reflexed, apex subrounded, middle lobe with a bright yellowish spot near the throat. Stamens 4, subequal, exerted under the upper lip; anther purplish brown. Ovary oblong, 1–1.5 mm long, glabrous, golden glandular at the top; style white, exerted, slightly longer than stamens, stigma equally 2-cleft. Fruits narrowly obovate, slightly drupaceous, shorter than the calyx, yellowish brown, only one seed fully developed.

Phenology:—Flowering from middle May to late June; fruiting from late June to August.

Distribution and habitat:—The natural distribution of the species is currently little known because it has been encountered only twice in the field, and we did not find any other specimens in the herbaria consulted. The species was discovered in tropical montane forests on the way from Kawlei to Shinsanku, Nawngmun Township, Putao District, Kachin State, northern Myanmar, at an elevation of 1000–1500 m, and observed as an epiphyte on the tree of Altingia excelsa ,

Etymology:—The specific epithet “ caridantha ” is derived from “ Caridea ” (commonly known as caridean shrimp) and “ anthos ” (means flower), indicating that the flower of the species superficially looks like a shrimp, especially its incurved corolla tube resembles the back of a shrimp.

Preliminary conservation status:— This species is only known from a single locality in northern Myanmar and we have not gotten a clear picture of its natural distribution and/or population status, making no adequate information to assess its risk of extinction directly or indirectly. Hence, we temporarily list the species as Data Deficient ( DD) according to the IUCN Red List Categories ( IUCN 2012). Further field surveys in Kachin State of Myanmar may provide more information on its abundance and/or distribution .

Taxonomic note:—In Premna , inflorescence structure and corolla shape have been tested to be of great significance for its taxonomy ( Li 2009). There are four basic inflorescence types observed in Premna , spike-like thyrses formed by sessile cymes, flat-topped corymbs formed by lax long petiolate cymes, capitula formed by dense short cymes, and conical panicles formed by lax cymes ( Li 2009). Three species having spike-like thyrses were recognized in Flora of China ( Chen & Gilbert 1994), viz., P. bracteata , P. interrupta , and P. racemosa Wallich ex Schauer (1847: 633) which has been reduced to a synonym of P. interrupta in Leeratiwong et al. (2009). In P. interrupta , sessile cymes form a single spike-like thyrse without branches ( Figs. 3D View FIGURE 3 , 4D & d View FIGURE 4 ), while in P. bracteata , the inflorescences have 2–4 pairs of secondary branches which are spike-like thyrses ( Figs. 3C View FIGURE 3 , 4C & c View FIGURE 4 ). A recently described new species, P. grandipaniculata ( Tan et al. 2018) , has spike-like thyrses too, which form an intricate panicle with 4–6 pairs of secondary branches and 1–3 pairs of tertiary branches for each secondary branch ( Fig. 3B View FIGURE 3 , 4B & b View FIGURE 4 ). Inflorescence of P. caridantha is most similar to P. grandipaniculata but the latter is characterized by having large broadly ovate to subrounded leaves with sharply acute apex ( Fig. 3B View FIGURE 3 ), while P. caridantha has oblong to ovate leaves with acuminate to acute apex. Besides, the corolla of P. grandipaniculata is nearly actinomorphic with extremely short and straight tube but that of P. caridantha is strongly 2-lipped with a short-incurved tube and a bright yellowish spot on the middle lob of the lower lip, which are distinct characteristics in the genus.