Two new species of Hiptage (Malpighiaceae) from Yunnan, Southwest of China

Abstract Hiptagepauciflora Y.H. Tan & Bin Yang and Hiptageferruginea Y.H. Tan & Bin Yang, two new species of Malpighiaceae from Yunnan, South-western China are here described and illustrated. Morphologically, H.pauciflora Y.H. Tan & Bin Yang is similar to H.benghalensis (L.) Kurz and H.multiflora F.N. Wei; H.ferruginea Y.H. Tan & Bin Yang is similar to H.calcicola Sirirugsa. The major differences amongst these species are outlined and discussed. A diagnostic key to the two new species of Hiptage and their closely related species is provided.


Introduction
Hiptage Gaertn. (Gaertner 1791) is one of the largest genera of Malpighiaceae with about 30 species of woody lianas and shrubs growing in forests of tropical South Asia, Indo-China Peninsula, Indonesia, Philippines and Southern China, including Hainan and Taiwan islands (Chen andFunston 2008, Ren et al. 2013). There are currently ten species of Hiptage recorded in Thailand (Sirirugsa 1987(Sirirugsa , 1991, ten species with seven endemic ones in China (Chen and Funston 2008) and 9 species in India (Srivastava 1992). So far, Ren (2015) recognised a total of 29 species in this genus.
The genus name, Hiptage, is derived from the Greek "hiptamai" which means to fly and refers to its distinctive three-winged fruit samaras, i.e. a larger middle wing and two smaller lateral wings, sometimes the dorsal wing is absent or present as a small crest, most species bear an elongated commissural gland on the calyx (Srivastava 1992, Anderson et al. 2006. Hiptage is also unique for having mirror-image flowers, with 1 long and 9 short unequal stamens (Ren et al. 2013, Qian et al. 2016. H. benghalensis (L.) Kurz is the most well-known species due to its attractive and fragrant flowers; it is often cultivated as a tropical ornamental plant in gardens (Anderson et al. 2006).
During floristic surveys in southern and south-western Yunnan from 2009 to 2017, some populations of Hiptage were discovered and some plants were cultivated in Xishuangbanna Tropical Botanical Garden (XTBG), Chinese Academy of Sciences (CAS). Based on detailed examination on the morphological and anatomical characters of the living plants and specimens and comparing them with the possible closely similar species, we found these populations representing two species distinct from the known 29 species so far (Sirirugsa 1991, Srivastava 1992, Chen and Funston 2008, Ren 2015. We draw a conclusion that those two species are new to science. Therefore, we described and illustrated the new species and compare them morphologically to its most similar congener.

Material and methods
Measurements and assessments of morphological characters of the two possible new species H. pauciflora Y.H. Tan & Bin Yang and H. ferruginea Y.H. Tan & Bin Yang were based on dried specimens in herbarium and fresh materials in field observations and cultivation plants flowered and fruited in XTBG. They were compared with the morphologically similar species H. benghalensis (Sirirugsa 1991, Chen andFunston 2008), H. multiflora (Wei 1981, Chen andFunston 2008) and H. calcicola (Sirirugsa 1987(Sirirugsa , 1991 in affinities inferred from protologues, type specimens and cultivation plants in XTBG. Images of type specimens were gathered from JSTOR Global Plants (http://plants.jstor.org) and Chinese Virtual Herbarium (http://www.cvh.ac.cn). Conservation status evaluations of the new species were based on the International Union for Conservation of Nature guidelines (IUCN 2012).

Diagnosis.
Hiptage pauciflora is similar to H. benghalensis in elliptic-oblong leaf blades, petal shape and size and also shares similarities with H. multiflora in having leaf marginal gland dots, sub-orbicular calyx glands and not decurrent to pedicel, obovate middle wing of samara, but differs from the former by lacking basal glands at the leaf base, calyx glands ovate or sub-orbicular to cordate, scarcely decurrent to pedicel, middle wing of the samara obovate-elliptic, lanceolate bracteoles 7-11 mm (vs. 1 mm); and differs from the latter by its fewer flowers, longer pedicels, without basal glands at the leaf base and elliptic sepals (vs. ovate).
Phenology. Hiptage pauciflora has been observed in flower at Xishuangbanna Tropical Botanic Garden under cultivation from the beginning of March and in fruit from March to April.
Etymology. The species epithet refers to its inflorescence with fewer flowers, usually 1-8 flowers.
Distribution and habitat. According to the introduction record, H. pauciflora was originally collected from Menglian, south-western Yunnan. Additional collections in the future may help to clarify its full distribution.
Phenology. Flowering in March and fruiting occurs from March to April. Etymology. The specific epithet is derived from its inflorescence rust-coloured hairy, ferruginous appearance.

Distribution and habitat.
There is only one population and less than 10 individuals known from the limestone areas in the Menglun Natural Reserve.
Conservation status. Since we have not discovered the wild population of this species in other places, very few details about its natural distribution and population status are currently obtained and the information is too inadequate to assess its risk of extinction. At present, it is proposed that it be considered as a taxon under the Data Deficient (DD) category on the basis of current IUCN Red List Categories and Criteria (IUCN 2012). Leaf blade ovate or ovate-elliptic to elliptic-oblong, less than 10 cm long, bracteoles lanceolate, 7-11 mm, leaf basal gland dots absent, inflorescence with fewer flowers, usually 1-8 flowers, pedicels 1.

Discussion
The zygomorphic or mirror-image flower of the Hiptage is a unique feature of evolutionary and biological importance that enhances adaptations (Ren et al. 2013, Qian et al. 2016. The presence or absence of calycinal glands calyx is an important characteristic and feature of the glands' shape and number, and whether it is adnate to pedicel or not is also a key diagnostic for species identification (Sirirugsa 1991, Srivastava 1992, Chen and Funston 2008. Morphologically, H. pauciflora shares certain characteristics with H. benghalensis in having elliptic-oblong leaf blades and sub-orbicular petals and also shares similarities with H. multiflora in having leaf marginal gland dots, sub-orbicular calyx glands and not decurrent to pedicel, obovate middle wing of samara. Hiptage ferruginea is similar to H. calcicola in elliptic leaf shape, hairy pedicels and hairy calyxes without glands, Middle wings of Samara obovate-elliptic, 1.7-2.5 × 1-1.3 cm oblong, elliptic or obovate-lanceolate, 3-5 × 1-1.6 cm obovate, 2.2-2.5 × 0.7-1.0 cm obovate, 1.7-2 × 1-1.2 cm oblong, 2-2.5 × 0.5-0.8 cm suborbicular petals. The detailed comparisons of the morphological differences amongst these taxa are given in Table 1 and evidence from morphological analysis supports the recognitions of H. pauciflora and H. ferruginea as two distinct species, respectively.