Didymocarpus sinoindicus N.S.Prasanna, Lei Cai & V.Gowda, 2020

Didymocarpus sinoindicus N.S.Prasanna, Lei Cai & V.Gowda View in CoL , sp. nov. Figs. 1, 2 & 3

Didymocarpus sinoindicus is morphologically similar to D. oblongus Wall. ex D.Don , but differs from it in having longer petioles (1.5–6.5 cm vs. 0.2–1.5 cm long), bicrenate or serrate leaf margins (vs. serrate to doubly serrate), and creamy-white to greenish-yellow (vs. purplish) corolla tube. It differs from D. hookeri C.B.Clarke in having shorter stems (2–8 cm vs. 4–17 cm long), and glabrous (vs. pubescent) corolla tubes. The new species differs from D. adenocalyx W.T.Wang in having glandular pedicels and calyces (vs. eglandular), and shorter corolla tubes (0.7–1 cm vs. c. 1.4 cm long).

Type: INDIA, Nagaland, Kiphire district, Mount Saramati, N 25 ̊45'11'', E 94 ̊59'26'', 2580 m, 29.08.2018, Preeti Saryan VG2018 NL3679 (holo BHPL!; iso ASSAM!) .

Perennial, lithophytic herbs. 6–15 cm tall. Dry season stem inconspicuous, juvenile leaves distinct, blades with much denser indumentum than when mature. Rainy season stem dark purple, erect, 2–8 × 0.2 cm, terete, densely puberulent with multicellular eglandular hairs, densely covered with globular golden pigment glands. Leaves 2–3 pairs, opposite and anisophyllous, decussate, whorled at the top of the stem; petioles terete, 1.5–6.5 cm long, eglandular pubescent and pigmented as on the stem; lamina ovate to oblong or falcate oval, 4–20 × 2– 10.5 cm, base cuneate or oblique, occasionally rounded, margins bicrenate or serrate; apex obtuse to acute; adaxial surface dark green, pubescent with multicellular eglandular hairs interspersed with globular golden pigment glands; abaxial surface light green, sparsely eglandular pubescent along the veins, glabrous otherwise, sparsely covered with pigment glands; midrib with 6–10 lateral veins on each side, depressed adaxially, raised abaxially. Inflorescences 1–4, pair-flowered cymes, 6–25- flowered, pedunculate, axillary towards the top of the stem or terminal; peduncle terete, 2–5 cm long, light green, pubescent with multicellular hairs, pigment glands present, glands dense between bracteoles and the peduncle; paired bracteoles present at each dichotomous fork; primary bracteoles (at first inflorescence fork) 2, cupular, ovate to orbicular, 0.6–1.2 × 0.6–1.0 cm, opposite, connate at base, light green, margins entire or sometimes crenate, glabrous, rarely pubescent towards margins, ventral surface sparsely glandular, veins visible when dried; secondary bracteoles (at subsequent inflorescence fork) cupular to navicular, ovate to suborbicular, c. 2 × 6 mm, connate at base, greenish-white, ventral surface sparsely glandular; pedicels 0.5–1 cm long, sparsely covered with gland tipped multicellular hairs, pigment glands present. Calyx campanulate, 4–6 mm long, creamy-white to greenish-yellow, basally connate, 5-lobed, to c. 1/5 of the length; lobes ovate to ovate-triangle, equal, 1–1.8 × 1–1.5 mm, covered with peltate pigment glands outside, glabrous inside. Corolla bilabiate creamy-white to greenish-yellow with purple striations on the limbs; tube 7–10 × 1.5–3 mm, broader at the base, narrow towards lobes, glabrous; corolla limb bilabiate, glabrous, eglandular, upper lip 2-lobed, lobes suborbicular, 1.5–2 × 1 mm, held at right angles to the lower lobes, creamy white, lower lip 3-lobed, lobes semiorbicular to ovate, 3–4 × 3–4 mm, creamy-white with purple blotch at the junction of the three lower lobes, purple striations extending from the base of each lobe towards the tip. Stamens 2, adnate to corolla, 5–6 mm from the base, inserted above the midpoint of the tube; filaments 0.8–1.5 mm long, glabrous; anthers c. 0.8 mm long, glabrous, dorsifixed, coherent by adaxial surfaces, exserted. Staminodes 2, inconspicuous or minimal, c. 0.15 mm long, adnate to corolla 5–6 mm from base. Disc tubular with undulating upper margins, 1–1.2 mm long, glabrous, persistent. Pistils 5.5–6.5 mm long. Ovary cylindrical, 3–3.5 mm long, stipe absent, covered with peltate pigment glands; style c. 2 mm long, glabrous; stigma peltate, pubescent. Capsules linear, bivalved, dehisce loculicidally, c. 1.4–1.6 × 0.15 cm, covered with glands; seeds unknown.

Flowering & fruiting: Flowering from July to September in India and April to August in China and fruiting from August to November in both India and China.

Habitat: Didymocarpus sinoindicus grows on moss covered, rocky cliffs in heavily shaded forests at an altitude of 2200 to 2600 m. In India, it occurs along with Rhododendrons in the temperate forests. In China, it occurs in evergreen broad-leaved forest along with Rhododendron delavayi Franch. , R. ovatum (Lindl.) Planch. ex Maxim. , Vaccinium sp. and Gaultheria griffithiana Wight ( Ericaceae ), Viburnum cylindricum Buch.-Ham. ex D.Don ( Caprifoliaceae ), Myrsine semiserrata Wall. ( Myrsinaceae ), Rubus lineatus Reinw. ( Rosaceae ) and a few other species of Theaceae and Fagaceae .

Distribution: Currently, it is known from only two locations in India and one location in China, all of them bordering Myanmar. In India, the type locality is near the base camp of Mount Saramati in Kiphire district in the northeastern state of Nagaland. There is a historical collection site on the nearby Japvo ridge in Nagaland. In China, it is found in Danzha Village of Tengchong in Yunnan Province. It is likely to be present in the high elevation areas of Sagaing and Kachin states of northern Myanmar due to its similar habitat and proximity to the type locality.

Etymology: The specific epithet ‘ sinoindicus ’ refers to the two collection localities from where the species has been collected and is known until now ( China and India). It also acknowledges the serendipitous, simultaneous description of this species from two different research groups from India and China which happened to arrive at the same conclusions.

Specimens examined: CHINA, Yunnan, Tengchong City, Houqiao Town, Danzha Village , Langyashan , 25̊30' N, 98̊17' E, elev. 2528 m, 09.10.2019, D. T. Liu et al. CL19005 ( KUN) . INDIA, Nagaland, Naga hills, Japvo ridge, 7200 ft (2194 m), 11.11.1949, F. Kingdon-Ward 19018 ( BM [ BM011026036 , BM011026038 ], E [ E00627990 ], NYBG [ NYBG02652121 View Materials digital image]) .

Conservation status: We found only a small population of five mature individuals at Mt. Saramati , Nagaland, India. This is a community protected area with very little anthropogenic disturbance. The current status of the population at the Japvo ridge locality, 100 km distant from the Mt. Saramati locality, is unknown. The collection from China is limited to only one location. Although there are suitable habitats in between the currently known locations, there is lack of systematic survey for a conservation assessment. Thus we categorize it as data deficient ( DD) following the IUCN guidelines ( IUCN, 2019) .

Notes: In 1949, the English botanist Kingdon-Ward collected a few specimens of Didymocarpus from the Japvo ridge of Nagaland, India which resembles D. sinoindicus ( F. Kingdon-Ward 19018). He had identified the specimens as Didymocarpus species based on vegetative structures and fruits, but failed to assign a species name due to lack of flowers.

This manuscript is an outcome of an unexpected collaborative work between two independent research groups from India ( NSP, PS and VG) and China ( DTL, SZD and LC). 69 years after Kingdon-Ward’s collection, the Indian group collected specimens in 2018 and the Chinese group in 2019. Coincidentally, both manuscripts were submitted for publication in the special issue of Rheedea on Gesneriaceae . Both the groups had described their respective new species using specific epithet that reflected the respective type localities (Saramati hills in India and Tengchong in China). Incidentally, the reviewers and the editor discovered the similarities in the two species and suggested for further study by the authors which has resulted in this collaborative work, and a collaborative description of D. sinoindicus . This study therefore illustrates the need for more collaborative floristic studies between India and China which will give us a better insight in our shared biodiversity, allow us to implement better conservation practices, and reduce taxonomic confusions.