Onosma fuyunensis (Boraginaceae), a new species from Xinjiang, China

Abstract Onosma fuyunensis, a new species of Boraginaceae from northern Xinjiang, China, is described and illustrated here. Onosma fuyunensis is similar to O. simplicissima and O. gmelinii; it differs in having a particularly bristly indumentum, unbranched stems, white and yellow corollas, anthers united only at base, and nutlets with a stipitate cicatrix. An updated key to the species of Onosma from Xinjiang and Altai Mountains is also provided.


Introduction
Onosma L. (Boraginaceae-Lithospermeae), one of the largest genera in Boraginaceae, is primarily distributed in the temperate zones of the Old-World, with the main center of diversity in the Irano-Turanian region (Weigend et al. 2016). In recent years, several new species of Onosma have been described (Riedl et al. 2004, Binzet and Orcan 2007, Kandemir and Turkmen 2010, Aytac and Turkmen 2011, Almasi and Ranjbar 2015, Tarimcilar et al. 2015, Binzet 2016a, Binzet 2016b, Cecchi et al. 2016, Binzet and Eren 2018, Dehshiri 2018, He et al. 2018, Mehrabian and Mozaffarian 2018, Mehrabian and Rad 2018, which increases the total number of Onosma species to nearly 240. The northeastern region of the geographic distribution of the genus ranges from Turkestan to Altai (Johnston 1951), with the Altai Mountains running through Russia, China, Mongolia and Kazakhstan. In this area, four species and one subspecies of Onosma have been described (Krylov 1907, Popov 1953, Rybinskaya 1997, Baitulin and Kotukhov 2011, Urgamal et al. 2014). Furthermore, five species and one subspecies of Onosma are recorded in Xinjiang (Riedl 1995, Zhu et al. 1995, Pan and Nurbay 2004, a region of China that includes the southern part of Altai Mountains.
In Flora of the USSR, Popov (1953) provided the classification of sect. Aponosma DC. and sect. Euonosma DC (subsect. Haplotricha Boiss. and subsect. Asterotricha Boiss.), which was a combination of Candolle (1846) and Boissier (1875). On a sectional level, the morphology of the calyx in fruit and of the leaf indumentum are considered as the main diagnostic characters, but recent molecular data does not support the monophyly of these sections or subsections (Cecchi et al. 2016, Nasrollahi et al. 2019. On a specific level, the morphology of the flowers, the indumentum inside the corolla, and the morphology of the filaments and anthers have demonstrated to be useful characters (Johnston 1951, Liu 1989. Nutlet and pollen morphology also may be important characters to clarify similar species in Onosma taxonomy. (Binzet et al. 2014, Mehrabian et al. 2012, He et al. 2018.
In the process of a taxonomic revision of Chinese Onosma species, the identification of specimens from Xinjiang was extremely confusing, especially those specimens collected from Fuyun and Qinghe County, Altay City. Some of the specimens were identified as O. simplicissima, while others were assigned to O. gmelinii. However, within this group of Onosma is clearly another distinct taxon with a combination of characters that could not be associated with either O. simplicissima or O. gmelinii. Further detailed literature examination and field trips to Northern Xinjiang convinced us that this neglected taxon has been mistakenly mixed within those two species for more than half a century. To our best knowledge, it is not any other known species from the Altai Mountains and nearby regions. Here, we clarify the confusion by describing and illustrating this new species. An updated key of genus Onosma from Altai Mountains and Xinjiang is also provided for further study.

Materials and methods
A total of 37 herbarium specimens of Onosma fuyunensis were collected from four populations in Northern Xinjiang, China in July, 2017. Type photos of accepted names and their synonyms from Xinjiang and adjacent regions were examined and compared along with 133 herbarium specimens from BNU, KUN, N, NAS, PE, XJA, XJBI, YUKU and 731 specimen pictures from BM, E, FL, K, KW, L, G, MO, MW, P and W. Images of morphological features were taken by Nikon digital camera with macro lens. Dried leaves, nutlets, and pollen grains were settled on stubs using double-sided adhesive tape and were coated with gold by Hitachi E-1045 ion sputter, photographed by Cam Scan Hitachi SU4800 Electron Microscope. For pollen studies, 30 pollen grains were measured for polar axis (P) and equatorial axis (E). Voucher information for the plant materials used was shown in Table 1. Terminology for pollen was used under Erdtman (1952) and Punt et al. (1994). The main characters for comparison of related species are presented in Table 2, which were measured by Image J 1.52a (Abràmoff et al. 2004). Conservation assessments were made according to the IUCN Standards and Petitions Committee (2019) guidelines.   Fig. 1B), having leaves with spreading bristles (Fig. 2 C-F, v.s. densely silky appressed pilose), larger nutlets (ca. 5 mm v.s. 2.5-3 mm), longer calyx (15-22 mm v.s. 6-13 mm) and corolla (22-27mm v.s. 18-20 mm). Also nearly to O. gmelinii Ledeb., but different through having obvious reticulate venation (v.s. obscure lateral veins), slightly elongating and straightening inflorescences in fruit (v.s. markedly elongating and straightening), longer and parallel calyx lobes in fruit (1.2-2 mm v.s. ca. 4mm, lobes converging), cream and pale yellow corolla (v.s. pale yellow), included anthers united only at base (v.s. united into a tube, Fig. 3D), nutlet with stipitate cicatrix and elongated, rectangular surfaces epidermis cells (v.s. complanate cicatrix and reticulate cells, Fig. 3A, F) and isopolar pollen grains (v.s. heteropolar, Fig. 3H).
Phenology. Flowering and fruiting occurs from May to July. Etymology. The specific epithet of the new species refers to its type locality, Fuyun County, Xinjiang, China.
Distribution and habitat. Onosma fuyunensis is mainly distributed in Fuyun County, Qinghe County and Altay Prefecture (Fig. 4), it is also known from W Mongolia near the border (Khovd aimag), according to the photo record by Peter Kosachev (http://www.plantarium.ru/page/image/id/128255.html). It prefers dry rocky screes and upland meadows along the hillside, from 500-1400 m a.s.l. Species growing nearby are: Echinops gmelinii Turcz, Goniolimon speciosum (L.) Boiss., Artemisia rutifolia var. altaica (Kryl.) Krasch. and Carex turkestanica Regel.    Conservation status. According to current data, Onosma fuyunensis grows in a large area of ca. 70, 000 km 2 between N Xinjiang and W Mongolia. Similar habitats are common in this area. During our field investigation, four large populations (at least 50 mature individuals) of this species were easily found even at the end of its flowering season. Onosma fuyunensis could be the dominant species in some screes and meadows. In this area, human activities are infrequent, and grazing pressure is low. Historical specimens of this taxon are also abundant (from 16 different locations). According to the IUCN Standards and Petitions Committee (2019) criteria, we justify a preliminary status of 'Least Concern' (LC). More accurate quantitative analyses should be used for assessment after more field works in the future.

Discussion
This species is widely distributed in the middle and low altitude mountains in the eastern part of the Altai Mountains. In the past 60 years, multiple specimens of this taxon have been collected; however, they were not recognized correctly.
According to its nature of indumentum, O. fuyunensis belongs to subsect. Haplotricha Boiss. Morphologically, in the color and shape of the corolla, this species is close to O. simplicissima. The upper part of the fresh corolla is milky white, and the part below the calyx is light yellow. The whole corolla turns pale yellow after drying. The filaments are slightly longer than the anthers, which are united only at base and not exserted from the corolla. The calyx of this species is longer, nearly half to 2/3 of the length of the corolla, while the calyx of O. simplicissima is shorter, only ca. 1/3 of the length of the corolla. There is a large difference in the vegetative features of the plants of this newly described species. O. fuyunensis is perennial herb with highly-developed rosettes, lacking sterile shoots, covered with long and spreading bristles, while O. simplicissima is subshrub with differentiation of flowering shoots and sterile shoots (without rosettes) and its indumentum is appressed.