Spiradiclis pengshuiensis (Ophiorrhizeae, Rubioideae), a new species from Chongqing, China

Abstract Spiradiclis pengshuiensis Bo Pan & R. J. Wang (Rubiaceae) is described as a new species from Chongqing in SW China. It is morphologically compared with Spiradiclis pauciflora L. Wu & Q. R. Liu because of their similarities in habit, pubescent surface, small leaf laminas and subglobose capsules. Its conservation status is evaluated as “VU” according to the IUCN categories and criteria.


Introduction
Th e genus Spiradiclis Blume (Rubiaceae) mainly distributed in the tropical and subtropical limestone areas of Southern China and Northern Vietnam. Geographically, the localities of Spiradiclis species can extend northward to Mt. Emei (29°33'N) in Sichuan province of China and southward to Central Java (ca. 7°10'S) of Indonesia. Th e genus comprise about 50 species and ca. 91% species can be found in China, the center of species diversity (Chen and Taylor 2011, Deng et al. 2014, Wu et al. 2015, Wang 2016. Spiradiclis species are usually similar to Ophiorrhiza L. because of their similar infl orescence and fl ower characters, but the former is characterized by globose or ovoid (vs. strongly laterally compressed in Ophiorrhiza) capsules.
During a botanical inventory in Pengshui County, the east of Chongqing Municipality, in 2013, the senior author found a striking Spiradiclis species growing on the dry cliff s. In order to get enough materials for morphological observation and comparison, we successively collected the vouchers during the fl owering and fruiting seasons in recent years. Th is new species can be readily distinguished from other Spiradiclis species in habit and fl owers and herein described and illustrated.

Material and methods
All materials were collected by ourselves and deposited at the herbarium of South China Botanical Garden, Chinese Academy of Sciences (IBSC). Th e morphological data were collected by a Digimatic Caliper (Mitutoyo, Japan).

Phenology
Flowering in November to next January, fruiting in December to February Flowering in March to June, fruiting in May to August stamens included; fi laments adnate to the lower corolla tube, ca. 1.5 mm long; styles 9-12 mm long; stigma ca. 0.5 mm long, red to brown, extended to corolla throat, not exserted. Short-styled fl owers: stamens extended to corolla throat, not exserted; fi laments adnate to upper corolla tube, ca. 0.5 mm long; styles ca. 5 mm long; stigmas ca. 1.5 mm long, included. Capsules subglobose, 3-5 mm in diam., with persistent calyx lobes, dehiscent septicidally and loculicidally; valves 4, ovate, 3-5 mm long. Seeds 15-20 per capsule, ca. 0.5 mm long, brown, irregular pyramid to cuboid, foveolate on surface. Phenology. Flowers from November to next January; fruits from December to next February.
Distribution and habitat. Spiradiclis pengshuiensis is known only from the type locality. Its habitat is on the cliff s nearby the A-Yi-He river but with very poor conditions. Conservation status. Only three small populations and less than 500 individuals of Spiradiclis pengshuiensis within 5 km 2 were found in the A-Yi-He Scenic Area. Th e tourist activity is the primary factor in the decline of populations. In addition, the plants always grow on the cliff s with little soil and insuffi cient water, which limited the development and dispersal of the species. Th erefore we assign a preliminary IUCN threat status of Vulnerable [VU,B2ab(ii,iii,iv)] to S. pengshuiensis (IUCN 2001).