Rhododendron microcarpum R. L. Liu et L. M. Gao, Sp.

Liu, Ren-Lin, Tang, Zhong-Bing & Gao, Lian-Ming, 2018, A new species of Rhododendron (Ericaceae) from Jiangxi of China based on morphological and molecular evidences, Phytotaxa 356 (4), pp. 267-275 : 271-273

Rhododendron microcarpum R. L. Liu et L. M. Gao, Sp. nov. ( FIGURE 3 ).

Rhododendron microcarpum R. L. Liu et L. M. Gao resembles R. ovatum (Lindl.) Planch. ex Maxim. , but differs from R. ovatum in the elliptic leaves, small leaves (2.56 ± 0.11 cm), flowers (lobes 1.3–1.6 cm long) and fruits (2.9–3.5 × 3.5–4.2 mm), short calyx (0.23 ± 0.003 cm) and pink-white corolla ( TABLE 2 , FIGURES 4 & 5 ).

Type: CHINA. Jiangxi: Yingpan Mountain, nortern side of Nanling Mountains , Ganzhou, elevation 1100–1600 m, 6 July 2017 (flower), R.L. Liu L-003 (holotype: L-003 , KUN ; isotype: GNU ).

Morphological description: Evergreen shrub, 0.5–1.5 m tall; branchlets glabrous or sparsely glandular pilose. Simple leaf; leaves densely aggregated at the terminal of branchlets; leaf blade leathery, broadly elliptic, 1.2–2.7 × 0.7–1.3 cm, apex acute and emarginated, mucronate, both surfaces glabrous, margin revolute and entire, base obtuse. Petiole glabrous, 4–5 mm long. Flower bud scales persistent, ovate, 4–5 mm long, glabrous, margin pubescent; Bisexual flower; flowers axillary at the terminal of a branchlet, 1 flower; Pedicel sparsely glandular hairs and tiny pubescence, 1.4–1.8 cm; calyx 5- lobed, 2–3 mm long, ovate, membranous, lobe base densely glandular hairs, lobe margin sparse glandular hairs and pubescence; corolla pink-white, rotated with a short tube, 3–4 mm long, 5-lobed, obovate oblong, obtuse, 1.3–1.6 × 0.9–1.1 cm, both inner and outer surfaces glabrous, upper lobe inner with dark-red spots; stamens 5, anther 1.5–2 mm long, filaments with pubescence at middle-base part, 1.3–1.5 cm long. Ovary ovate, ca. 1.5mm high, with sparsely glandular hairs, 5-locular; style slender, glabrous, 1.7–1.9 cm long, slight longer than filament, often exserted corolla, stigma small. Capsule small and broadly ovoid, axile placenta, 2.9–3.5 × 3.5–4.2 mm, sparsely glandular without pubescent.

Additional specimens examined: China. Jiangxi: Yingpan Mountain , Ganzhou, 6 July 2017, R. L. Liu, L-001 , L-002 , L-004 ( GNU) ; ibid., 25 July 2016, R. L. Liu, L20160725003 , L20160725004 , L20160725005 , L20160725007 , L20160725009 ( GNU) ; ibid., 10 August 2001, R. L. Liu, L20010810-001 ( GNU) .

Distribution and ecology: To data, R. microcarpum has only been found in a unique locality, Yingpan Mountain (26°00’ 42” N; 114°07’ 67” E) located at northern side of Nanling Mountains, Southwest Jiangxi, China. This species grows in the montane pine forest ( Pinus taiwanensis forestry) at an elevation between 1100 and 1600 m ( FIGURE 1 ).

Phenology: R. microcarpum flowers in early July, and fruits matured during August to September.

Etymology: The specific epithet refers to its distinct morphological feature of small size of fruits compared to its closely related species.

Conservation status: Since 1999, many surveys have been carried out in Yingpan Mountain, and the adjacent region of Nanling Mountains and Luoxiao Mountains with numerious plant specimens collected - including those of Rhododendron . We have examed all the specimens of Rhododendron collected in this region presrved in several herbaria in Southern China. The new species R. microcarpum can be considered a restricted distribution species, and no additional localities of the new species has been discovered outside the type locality. On the other hand, the habitat of the new species is in some degree of destruction, and the populuation is facing endangered under the scenrio of climate change and human activities. According to the criteria of IUCN, R. microcarpum should be an endangered (EN) species.

Figures

FIGURE 1. Geographical distribution range of the three species of Rhododengdron.

FIGURE 3. Rhododendron microcarpum (from the holotype, drawn by Ling Wang from KUN). A, Flowering branches with leaves. B, Flower. C, Scales and unopened flower. D, Flower branch and pistil. E, Calyx. F, Stamen. G, Corolla.

FIGURE 4. Rhododendron microcarpum. A, B, Habitat.C, Flowers and leaveas. D, Axillary flower. E, Stamens and filaments.F, Leaveas and small fruits.

FIGURE 5. Comparison of leaves and friuts between Rhododendron microcarpum and R. ovatum. A-1, Leaves of R. ovatum;A-2, Leaves of R. microcarpum. B-1, Fruits of R. microcarpum; B-2: Fruits of R. ovatum.