Primula brachystoma W. W. Sm.

Jiang, Xiao-Qi, Zhang, Na & Wu, Zhi-Kun, 2023, Rediscovery of Primula brachystoma (Primulaceae), a rare species endemic to Gaoligong Mountain of Chinese-Burma frontier, PhytoKeys 227, pp. 35-42 : 35

Primula brachystoma W. W. Sm.

Primula brachystoma W. W. Sm. in Notes Roy. Bot. Gard. Edin., xiv, 35 (1923); W. W. Sm. et Forrest, ibid., xvi, 17 (1928), and in Journ. Roy. Hort. Soc. London, liv, 43 (1929); W. W. Smith et Fletcher in Trans. Bot. Soc. Edinb. xxxiii: 166 (1941). Type: Burma, Shing Hong region, 20 June 1920, R. J. Farrer 1635 (holotype E! E00024386; isotypes BM, BM000996925, K, K000732874).

Description.

A perennial herb, completely glabrous and efarinose, with numerous robust roots. Leaves forming a rosette; leaf blade oblanceolate to sublanceolate, 6-12 cm long, 2-4 cm broad, acute and shortly apiculate at the apex, petiole very short or as long as 1/3 of the blade, base attenuate with broadly winged petiole, margin regularly fine dentate, teeth triangular, apex acute and subulate, leaf abaxially with prominent midrib and conspicuous lateral veins, and inconspicuous mesh vein. Scapes slightly slender, 15-25 cm long; umbels 1 (or rarely 2), 2-7 flowered. Bracts linear-lanceolate, 0.6-0.8 cm long. Pedicel slightly recurved when flowering, erect when fruiting, 0.8-1 cm long in flowering, up to 1.5 cm long in fruiting. Calyx campanulate, green, 5-7 mm long, with 5 ribs, splitting slightly less than 1/3 of its full length, lobes triangular, apiculate at the apex. Flowers homostylous or heterostylous in different populations, corolla funnel-shaped, yellow, tube 8-10 mm long, with a marked annulus, limb 1-1.5 cm wide, lobes sub-quadrangular to obovate, 4-5 mm long, shallowly notched; homostylous flowers: the stamens are inserted in the middle of the corolla tube, filament ca. 0.5 mm long, anther ca. 0.8-1 mm long, yellowish white, the style reaches to the level of the stamens; heterostylous flowers: in long-styled flowers the style nearly reaches the annulus and the stamens are inserted towards the base of the corolla, in short-styled flowers the stamens are inserted slightly below the annulus and the style is shorter than the calyx, the filament and anther as those in homostylous flowers. Capsule globose, green in young fruiting time and pale purple in mature fruiting time, 5-6 mm long, as long as or slightly shorter than calyx, 4-5 mm in diameter.

Distribution and habitat.

It is found on Gaoligong Mountain on the border between China and Burma. One homostylous population is at the type locality Shing Hong of Burma and two homostylous populations are at Sandui and Tsuga of Gongshan county, China; the other two heterostylous population are at Sibali and Luodigolu, Yaping of Fugong county, China. It grows along moist streams or on wet grassy slopes at forest margins, 2500-3000 m above sea level.

Additional specimens examined.

China, Gongshan Xian , Dulongjiang Xiang: Sandui [27°42′56.112′′N, 98°25′24.048′′E, 2580 m], May 2015, ZKWU 2015036 (KUN!) ; China, Fugong Xian , Lishadi Xiang: Yaduo Cun [27°10′36′′N, 98°44′55.9′′E, 2830 m], 6 August 2005, Gaoligong Shan Biodiversity Survey 26554 (KUN!) ; China, Fugong Xian , Lumadeng Xiang: Yaping Cun [27°10′3′′N, 98°46′17.7′′E, 2510 m], 16 August 2005, Gaoligong Shan Biodiversity Survey 28479 (KUN!) ; China, Fugong Xian , Lishadi Xiang: Yaduo Cun [27°10′1.8′′N, 98°46′24.8′′E, 2520 m], 16 August 2005, Gaoligong Shan Biodiversity Survey 28435 (KUN!) ; China, Gongshan Xian : Tsuga on the way from Gongshan Xian to Dulong River, east slope of Gaoligong mountain, 26 July 1982, Qinghai-Tibet team 8648 (PE, KUN!) .

Provisional conservation status.

Primula brachystoma is neither listed in the IUCN Red List ( IUCN 2022), nor in the threatened Species List of China’s Higher Plants ( Qin et al. 2017). The authors have conducted field surveys in the regions of Gaoligong mountains many times and discovered only three populations of Primula brachystoma in Fugong county and Gongshan county. Surveys from other plant hunters also didn’t find more populations in this area. We estimated the extent of occurrence of the species to be less than 1000 km2, and the adult individuals as fewer than 1000. The sites where the known populations grow are also places for grazing, so they face a strong threat from human activities. Accordingly, we evaluate the species as Endangered (EN B1ab(iii)), considering the IUCN standards ( IUCN Standards and Petitions Committee 2022).