Spiradiclis longanensis, a new species of Rubiaceae from China

Abstract A new species of Spiradiclis (Rubiaceae) was found during our field trip to Guangxi, China, and is described here as Spiradiclis longanensis R. J. Wang. This species is readily distinguishable from other prostrate and decumbent species of the genus described previously by dense pubescence all over the plant, 5–20 small flowers per cymose, linear calyx lobes, and tubular corolla. The conservation status of VU was preliminarily assessed according to IUCN categories and criteria.


Introduction
Th e genus Spiradiclis Blume belongs to the tribe Ophiorrhizeae in the subfamily Rubioideae (Bremekamp 1952, Bremer andManen 2000), and comprises approximately 45 species (Wang et al. 2015). Its members are perennial herbs or subshrubs and usually grow at the entrances of caves or mountain cliff s in the limestone area of Southern China and Northern Vietnam (Lo 1999, Wang 2002, Chen and Taylor 2011. Th ey favor moist and shaded habitats, usually with ferns, Gesneriaceae, Begoniaceae, and Loganiaceae plants. Spiradiclis species are characterized by having usually 5-merous fl owers and globose or ovoid capsules in a cymose or paniculiform infl orescence with dichasial or scorpioid axes (Deng et al. 2014).
During a fi eld investigation in 2013, we found a semi-erect and hairy herb, which was similar to Spiradiclis danxiashanensis R. J. Wang in habit and leaf size. Unfortunately, the voucher (R. J. Wang & S. J. Deng 2324, IBSC) was only a vegetative individual at that time. Th e specimens with fl owers and fruits were eventually collected after our subsequent collecting in diff erent seasons. Th e 5-merous distylous fl owers and ovoid to subglobose capsules in a cymose demonstrated that the plant was a true member of Spiradiclis. Our comprehensive examination showed that the fl owered and fruited specimens represent a new and undescribed species of Spiradiclis.

Material and methods
All materials were collected by ourselves and deposited at the herbarium of South China Botanical Garden, the Chinese Academy of Sciences (IBSC). Th e leaf materials were carefully taken from the specimen R.J. Wang & Q. Liao 2592 (IBSC) and washed three times with 95% ethanol and then mounted on copper stubs. Samples were sputter-coated with gold particles for 15 min using a JEOL JFC-1600 AUTO FINE COATER. Scanning Electron Microscope (SEM) observation was carried out by JEOL JSM-T300. Digital images of the coated leaf surface were taken during the observation.
Distribution. Known only from the type locality. Th e plants grow in the entrances of limestone caves or moist cliff s of hill sides.
Ecology. Flowering in May-June and fruiting in June-August. Conservation status. Th e number of S. longanensis was less than 500 individuals within an area of less than 5 km 2 ; however we know that the present fi eld investigation is in a very low density and the evaluation we made here was based on all the available information up to now. We therefore assign a preliminary IUCN threat status of Vulnerable (VU,B2ab(ii,iii,iv); D) to S. longanensis (IUCN 2001). Th e populations are probably prone to the eff ects of human activities or stochastic events in future, because the plants grow nearby the main traffi c road or rice fi eld.
Additional specimens examined ( Discussion. Similar to Spiradiclis longanensis in this genus, S. danxiashanensis, S. guangdongensis, S. hainanensis and S. umbelliformis are all in prostrate or decumbent habit, but their leaf laminas, infl orescences, calyx lobes, and fl owers are diff erent from S. longanensis and can easily be distinguished. Th e latter four species usually have rounded, orbicular, or ovate leaf laminas in 1-2.5 mm long and with 3-5 unobvious secondary veins each side, and their infl orescences often include 1-3 salverform and never condensed fl owers, with ovate to lanceolate calyx lobes.
of Botany, Guangxi Zhuangzu Autonomous Region and Chinese Academy of Sciences for their kind help during our fi eld investigation; Dr. Bine Xue and Miss Shuangshuang Zhu for helpful comments on the manuscript.