Pseudostellariawuyishanensis, a new species of Caryophyllaceae from Fujian, China

Abstract Pseudostellariawuyishanensis, a new species from the Wuyishan National Park, Fujian, China, is described and illustrated. Morphologically, Pseudostellariawuyishanensis resembles P.heterantha. However, the new species can be distinguished by presence of stolons, 1 line of hairs on the stem, smaller leaf blades, shorter pedicels, and ovary with 2 styles.


Introduction
Pesudostellaria Pax is a small genus that belongs to the tribe Alsineae in Caryophyllaceae (Bittrich 1993;Tang et al. 1996). This genus can be easily distinguished from other genera in Caryophyllaceae from the presence of the flesh root tuber. In addition, the vast majority of species in the genus have cleistogamous flower and chasmogamous flowers that have petals with two sections (Zeng et al. 2016). Some recent molecular studies show that this group is non-monophyletic which includes a new described genus Hartmaniella and 2 species Stellaria americana (Porter & B.L.Rob.) Standl. and Arenaria przewalskii Maxim. nested within Pseudostellaria (Greenberg and Donoghue 2011;Zhang et al. 2017). Russian botanist Turczaninow (1842) first used Krascheninikovia Turcz. ex Fenzl for this genus, but this name was in fact a previous synonym for Eurotia Adans and did not comply with the international nomenclature regulations. Pseudostellaria was established by Pax in 1934 as the new name, which has been used until now (Schischkin and Komarov 1936;Ohwi 1937;Mizushima 1965). Currently, the genus is represented by ca.22 accepted species that are widely distributed all over the world, with 20 species in eastern and northern Asia, 1 species in Europe, and 1 species in North America. (Zeng et al. 2016;Zhang et al. 2017).
Since the turn of the 21 st century, 3 new species of Pesudostellaria have been established in China. Jin and Ding (2003) described P. zhejiangensis X.F Jin & B.Y Ding from the Zhejiang province based on its decumbent creeping stems, obtuse petals, and compressed seeds with a narrow wing. Lian (2009) Ren based on the regular variation in its floral morphology from stem apex to base. Xia et al. (2011) described P. tianmushansis Xia et al. based on its several tubers in a row, obovate with a bi-lobed apex petal and tubercles awned seeds. 12 species of Pesudostellaria have been recorded in China out of which 5 species are endemic.
During an investigation of wild plants in Fujian Province, southeastern China, that took place in May 2019 and October 2020, an unknown species of Pseudostellaria was collected from the deciduous broad-leaved forest in Wuyishan National Park. We found that it resembles P. heterantha Pax but has stolons, 1 line of hears in the stem, smaller leaves, and shorter pedicels. Therefore, we established it as a new species.

Material and methods
All general morphological data were obtained by observation of specimens during fieldworks and AU, FJIDC, IBSC, KUN, LE herbaria. Terminologies used in the present study follows the Flora of China (Lu and Rabeler 2001)  Diagnosis. Pseudostellaria wuyishanensis can be distinguished from P. heterantha by several morphological features and distribution (Table 1). P. wuyishanensis has stolons (vs. no stolon in P. heterantha), 1-1.6 × 0.5-0.7 cm (vs. 2-2.5 × 0.8-1.2 cm in P. heterantha) leaf blade, ca. 2 cm long (vs. 3-3.5 cm long in P. heteranth) pedicel and is 6-7 cm tall with 1 line of hairs (vs. 8-15 cm tall with 2 lines of hairs in P. heterantha). P. wuyishanensis only distribute in Wuyishan National Park, Southeastern China (vs. Northern and Southwestern China in P. heterantha) Description. Plants perennial. Root tubers green, fusiform, 0.4-0.6 × 0.2-0.3 cm. Stem erect, 6-7 cm tall, slender, unbranched at base, apex false dichotomous branched, stoloniferous, with 1 line of hairs. Leaves opposite, entire, 1-1.6 × 0.5-0.7 cm; proximal middle leaves oblanceolate, base attenuate into a petiole, apex acute; distal leaves ovate, shortly petiolate, membranous, both surfaces glabrous, the adaxial green, the    Phenology. Flowers were observed in June. Conservation status. There is only one known location and fewer than 50 individuals of P. wuyishanensis found during our fieldworks in the Wuyishan National Park in both 2019 and 2020. But the investigation has not been through enough to fully understand the species natural distribution. According to IUCN Red List criteria (2012), this new species should be assessed as Data Deficient (DD; criteria B1ab(i-v) + 2ab(i-v)).
Etymology. The specific epithet 'wuyishanensis' refers to Wuyishan National Park, the locality of the type collection.

Discussion
The new species morphologically resembles P. heterantha in the leaf shape, terminal chasmogamous flowers with pilose pedicel, and white emarginate petal. The two taxa differ in that the stem of P. wuyishanensis is shorter, conspicuously stoloniferous, apex false dichotomous branched, and only has 1 line of hairs, while that of P. heterantha is longer, solitary, branched at base, and has 2 line of hairs; the leaf blades of P. wuyishanensis is smaller and the pedicel is shorter. (Table 1). Ohwi (1937) regarded P. maximowicziana (Franch. & Sav.) Pax and P. himalaica (Franchet) Pax as the synonym of P. heterantha. The view was also approved by Mizushima (1965) and Lu (1998). However, some research results published in recent years do not support such a view (Chen et al. 2014;Zeng et al. 2016;Zhang et al. 2017). Zeng et al. (2016) suggested taking P. maximowicziana, P. himalaica, and P. heterantha as independent species respectively. None of the 3 species were collected in Fujian province or the surrounding area.
We only found two Pseudostellaria sp. specimens, IBSC 0149273 and IBSC 0149274 (Fig. 3) were collected in the Wuyishan National Park. Former researchers have identified them as P. rupestris (Turczaninow) Pax or P. heterophylla (Zeng et al. 2016). Morphologically, we found that the arrangement, shape and hairs of the leaves of these specimens were completely different from those two species, and the morphology of each part was consistent with P. wuyishanensis. In addition, the distribution location of P. rupestris was far away from the collection site. Considering all the factors, we believe that these specimens are in fact P. wuyishanensis.