Ardisia rubricaulis S.Z. Mao & C.M. Hu, 2013

Mao, Shi-Zhong & Hu, Chi-Ming, 2013, Ardisia rubricaulis sp. nov. (Primulaceae) from Guangxi, China, Phytotaxa 138 (1), pp. 39-42 : 39-41

Ardisia rubricaulis S.Z. Mao & C.M. Hu , sp. nov. ( Fig. 1 )

Type: ⎯ CHINA. Guangxi: Jingxi Xian, Sanhe village , 23º 12 ’ 06.45 ’’ N, 106º 03 ’ 41.14 ’’ E, 995 m elev., 28 May 2009, S. Z . Mao 030 (holotype: IBSC, isotype: IBK) .

Ardisiae maculosae Mez subsimilis, a qua imprimis inflorescentiis lateralibus, ferrugineo-puberulis, foliis subtus et lobis corollae densissime nigro-punctatis differt.

Evergreen shrub, 1 − 1.7 m high; branchlets deep reddish brown, ferrugineous and glandular puberulent when young. Leaves alternate, ± crowded towards the upper part of branchlets; petioles 0.7 − 1 cm long, glabrous; leaf blade oblong-elliptic, 12 − 16 by 2.2 − 3.4 cm, base cuneate, apex acute, margins subentire, with indistinct marginal glands (vascularized nodules), papery; glabrous adaxially, sparsely and minutely lepidote abaxially, glandular dots numerous, black, scattered, more distinct on abaxial surface; lateral nerves 12 − 18 on each side, with short intersecondary veins, angle to the midrib about 50°, upwards arcuate, anastomosing at margin, not forming a marginal vein; secondary veins slender, prominent on abaxial surface. Inflorescence a simple subumbellate-corymb, 4 − 5 crowded near apex of branches, in appearance of a compound terminal corymb, after anthesis the terminal bud of the branches continue apically into a leafy shoot, therefore at fruiting the infructescences are lateral at the base of the young shoots. Peduncle 2 − 4 cm long, ferrugineous puberulent; rachis very short, ca. 3 mm long, bearing 5 − 6 subumbellate flowers. Pedicels 7 − 10 mm long, ferrugineous puberulent. Calyx ca. 3.5 mm long, deeply split to near to the base; lobes elliptic, ca. 3 mm long and 2.2 mm wide, apex rounded, sparsely black-punctate. Corolla purplish, ca. 5.5 mm long, split near the base; lobes elliptic, 5 mm long and 3.2 mm wide, apex acute, dotted with dark glands on both surfaces. Anthers lanceolate, 3 mm long, apex acute, black-punctate on dorsal surface, opening by lateral slits; filament very short, ca. 0.6 mm long. Ovary ovoid, c. 1 mm in diameter, narrowed upward to the style; style ca. 4.5 mm long; ovules 6 − 10, in 1 or 2 irregular series on placenta. Fruit depressed globose, c. 6 mm in diameter, scarlet when mature.

Etymology: ⎯ The specific epithet rubricaulis highlights the prominent reddish brown colour of the stem.

Distribution, habitat and phenology: ⎯ Ardisia rubricaulis is so far known only from the type locality on limestone hills of Sanhe village (23º 12 ’ 06.45 ’’ N, 106º 03 ’ 41.14 ’’ E), Jingxi Xian, Guangxi, China. It grows in dense evergreen forest on slopes of limestone hills, at 995 m elevation. The flowers are reddish purple and appear in May.

Conservation status: ⎯ Only one population with about 30 individuals was found around the type locality. Ardisia rubricalulis should clearly be classified as Critically Endangered ( CR) ( B2 abiii), according to IUCN red list criteria ( IUCN 2001). Since 2009 an ex situ conservation programme has been carried up in the Guangxi Botanical Institute. The new species has been introduced and cultivated in the garden of the institute, and flowers freely .

Additional specimen examined (paratype): ⎯ China: Guangxi, Jingxi Xian, Sanhe village , 23º 11 ’ 54.90 ’’ N, 106º 03 ’ 50.72 ’’ E, 1079 m elev., 12 January 2013, S. Z . Mao 183 ( IBK) .

Discussion: ⎯ Ardisia is one of the largest genera of the Primulaceae . The first comprehensive taxonomic treatment of this genus was conducted by Mez (1902). He treated 235 species and divided the genus into fourteen subgenera, of which five are confined to Americas, the other nine are limited to Asia, Australasia, and the Pacific Islands. Since then many of new species have been described, and recently, Taton (1979) included the African genus Afrardisia Mez (1902: 183) in Ardisia ; Stone (1993) established a new subgenus Scherantha Stone, and Larsen & Hu (1995) reduced the genus Tetrardisia Mez (1902: 189) to Ardisa but treated it as a subgenus. Thus, in Asia the number of subgenera has increased to eleven and the species number, according to published and reliable unpublished Floras and checklists, is about 435 ( Sleumer 1988; Stone 1989a, 1989 b, 1990; Chen & Pipoly 1996; Hu & Vidal 2004). Of all the subgenera, Crispardisia Mez (1902) is the most distinguished one, uniquely characterised by leaves with marginal glands (vascularized nodules), and even can be easily recognized in sterile material. The new species superficially resembles A. maculosa Mez (1902: 146) , a species erroneously included in A. virens Kurz (1877: 575) by the authors of “Flora of China ” ( Chen & Pipoly 1996), but a recent study ( Hu 1999) proved that A. virens is a synonym of A. polysticta Miquel (1861: 576) . So, while these species are closely related, they can be distinguished from one another by the following key.

Key to Ardisia rubricaulis and its closely related species in China and Vietnam

1. Inflorescence of several simple subumbellate corymbs, lateral near apex of branches, which is terminated by a vegetative bud; branchlets and peduncles covered with rusty glandular short hairs; sepals and petals densely black-punctate ............................................................................................................................................................. A. rubricaulis

- Inflorescence simple or compound, consisting of a terminal umbel, with or without branches below; branchlets and peduncles glabrous or glabrescent; sepals and petals scarcely or sparsely black-punctate .......................................... 2

2. Corolla-lobes and leaves distinctly black-punctate ...................................................................................................... 3

- Corolla-lobes and leaves not or scarcely punctate........................................................................................................ 4

3. Calyx-lobes ovate, more or less acute ............................................................................................................ A. crenata

- Calyx-lobes oblong to suborbicular, apex rounded .................................................................................... A. polysticta

4. Leaves with 4–8 marginal glands on each side; sepals ovate to ovate-oblong, broadest at base ............... A. hanceana

- Leaves usually with 13 − 20 marginal glands on each side; sepals oblong, more or less narrowed at base A. maculosa

Figures

FIGURE. 1. Ardisia rubricaulis. A. flowering branch; B. flower bud; C. calyx; D. corolla opened up showing stamens; E. dorsal and ventral view of anthers; F. pistil. A−F drawn from S.Z. Mao 030. Drawing by Liu Yun-Xiao.