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Sorbus gongshanensis (Rosaceae), a new species from the Hengduan Mountains, China
expand article infoMeng Li, Xin-Fen Gao§, Jing Tian|, Wen-Bin Ju§
‡ Nanjing Forestry University, Nanjing, China
§ Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
| Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
¶ Sino-Africa Joint Research Center, Chinese Academy of Sciences, Wuhan, China
Open Access

Abstract

Sorbus gongshanensis sp. nov., a new species from the Hengduan Mountains China, is described and illustrated. It is similar to S. kurzii from China (Yunnan & Xizang), Nepal, and Sikkim in the size of the leaflets, glabrous veins, persistent (sometimes) herbaceous stipules and reddish brown villous inflorescences and red fruits, but differs in its serrate leaflet margins toothed in the distal half or often almost to their base, reddish brown villous to glabrous hypanthium and reddish brown villous infructescences, among other characteristics.

Keywords

Flora of China, taxonomy, Yunnan, Xizang

Introduction

Sorbus L. sensu lato (s.l.; Rosaceae) comprises about 260 species distributed in the temperate zone of the Northern Hemisphere (Aldasoro et al. 1998; Lu and Spongberg 2003; Zika and Bailleul 2015; Sennikov and Kurtto 2017). Both molecular (Campbell et al. 2007; Lo and Donoghue 2012) and morphological evidence (Zheng and Zhang 2007) suggests that Sorbus s.l. is polyphyletic. Sorbus sensu stricto (s.s.) includes ca. 80 species and is characterized by pinnately compound leaves. Recent molecular study of Sorbus s.s. suggests that the most recent common ancestor originated in eastern Asia (Li et al. 2017). The greatest diversity of species of Sorbus s.s. (ca. 60 species) is found in the mountains of southwestern China (principally the Hengduan mountains) and adjacent areas of Myanmar, Nepal, and the eastern Himalaya (Long 1987; Lu and Spongberg 2003; McAllister 2005; Watson and Manandhar 2012). This region is one of the world’s biodiversity hotspots, as it also is for the genus Sorbus (Myers et al. 2000; Li et al. 2017).

While studying Sorbus for the Flora of Pan-Himalaya Project, we found several accessions from Yunnan and Xizang, China, at the Harvard University Herbarium (GH) that were markedly different from other species of Sorbus. After detailed morphological examination, field investigation and literature study, it was concluded that these specimens represent an undescribed species, which we name S. gongshanensis. The description of S. gongshanensis is based on dried herbarium specimens stored at GH (all herbarium acronyms in this paper follow Thiers 2019).

Material and methods

Morphological study was based on specimens deposited in the following herbaria: A, BM, CAS, CDBI, G, GH, K, KUN and NF. Macroscopic descriptions were based on the specimen sheets and notes made in the field. Detailed observations were conducted using an optical microscope. For scanning electron microscopy (SEM), dried pollen grains and stomata were mounted on metal stubs and sputtered with technical gold, and then were observed under Phenom proX SEM at 10 kV accelerating voltage at the Chengdu Institute of Biology, CAS. Pollen grains come from the field collection from Motuo [China, Xizang, Meng Li 00281 (NF)]. Terminology of descriptive terms followed Flora of China vol. 9 (Lu and Spongberg 2003). Conservation assessment was based on the known distribution data and followed the IUCN red list category criteria (IUCN 2017).

Results

Taxonomic description

Sorbus gongshanensis Xin-Fen Gao & Meng Li, sp. nov.

Figs 1, 2

Type

China. Yunnan: Gongshan County, Bingzhongluo Xiang. Vicinity of Fucai, on the north side of Nianwaluo River, ca. 10.8 direct km of Bingzhongluo, east side of Gaoligong Mountains, 28°0.47'N, 98°31.11'E, alt. 2780 m, 1 Sept. 2006. Gaoligong Shan Biodiversity Survey (2006) 31749 (holotype: GH; isotypes: CAS, KUN).

Diagnosis

Similar to S. kurzii, but differs in its serrate leaflet margins toothed in the distal half or often almost to their base, reddish brown villous to glabrous hypanthium and reddish brown villous infructescences.

Description

Shrubs or trees, 2–3 m tall. Bark gray. Branchlets tomentose when young, glabrous when old. Buds ovoid. Leaves pinnately compound, 8–10 × 5–5.5 cm; petiole 1.5–3 cm long; stipules membranous, caducous; rachis slightly winged, sulcate, sparsely tomentose; leaflets 2–4 pairs, opposite, elliptic, oblong to oblong-ovate, 2.8–3.5 × 1–1.5 cm, length/width ratio 2.4–3, surfaces essentially glabrous or sparsely (moderately) villous at flowering, usually glabrescent thereafter; blade paler abaxially, dull green adaxially; lateral veins 8–11 pairs, margins serrate, in the distal half or often almost to their base; base rounded or oblique, apex acute. Inflorescences corymbose, 4–5 × 2–3 cm, 3–15 flowered, sparsely reddish brown villous; stipules semi-orbicular, 0.5–0.8 × 1–1.3 cm, herbaceous, persistent in fruit; pedicels sparsely reddish brown villous. Flowers 6–8 mm in diam.; hypanthium reddish brown villous or glabrous, sepals 1–1.5(–2) mm long, margins entire; petals white, orbiculate to obovate, 3–4 mm long; stamens 15–20; carpels 1/2 adnate to hypanthium, styles 3–5. Infructescences sparsely reddish brown villous; pomes red, globose to subglobose, 6–8 mm in diam.; sepals inconspicuous, incurved when fruiting. Seeds brown, ovoid-lanceoloid, 3–4 × 1.2–1.5 mm, slightly asymmetric.

Figure 1. 

Main morphological characters of Sorbus gongshanensis A flower, longitudinal section B fruiting branch C fruit, longitudinal section D fruit, cross section.

Figure 2. 

Sorbus gongshanensis A habit B stipules and reddish-brown hairs on infructescences C leaves D stomata of abaxial blade surface E inflorescence F perprolate shape pollen, length of polar axis (33.03 ± 2.67 μm) and equatorial (16.61 ± 2.44 μm) diameter G striate-perforate ornamentation of pollen grains.

Etymology

The specific epithet refers to the type locality, Gongshan County.

Phenology

Flowering May–July, fruiting September–October.

Distribution and ecology

Sorbus gongshanensis is known from the Yunnan & Xizang Province, China (Fig. 3). It grows in broad-leaved forests or on rocky slopes; 2500–3000 m.

Figure 3. 

Geographical distribution map of Sorbus gongshanensis from Yunnan and Xizang province, China.

Specimens examined

China. Yunnan: Gongshan County, Cikai Xiang, east side of Gaoligong Mountains, along the Danzhu River, on the roadside from Nu Jiang to Danzhu, 27°37.82'N, 98°37.30'E, alt. 2650 m., 2 July 2000. Li Heng 11905 (GH, CAS, KUN). Xizang: Motuo County, 80k to Galung La, 29°42.30'N, 95°34.24'E, alt. 2782 m., 2 June 2015. Meng Li 00281 (CDBI, NF).

Conservation status

The distribution of S. gongshanensis is based on three collections. The collection notes mention that S. gongshanensis is occasional in forests among boulders. There is no direct or indirect information about its current conservation status or possible threats. We therefore assign the conservation status of S. gongshanensis as ‘Data Deficient (DD)’ according to the IUCN red list criteria (IUCN 2017).

Discussion

Sorbus species show a high level of similarity in flower structure and color. The numbers of leaflets and fruit color are also fairly consistent across the group (Li et al. 2017). The number of leaflet pairs in Sorbus range between 2 and 21 pairs, and fruit color ranges between white, pink, red and orange-red (Lu and Spongberg 2003). While useful floral morphological characteristics are limited, pairs of leaflets, leaflet size, serra position, stipule shape and fruit color can provide valuable information for the identification of Sorbus at the species level.

A few species in the Hengduan Mountains have few pairs of leaflets. This group includes S. helenae Koehne (3–4 pairs), S. insignis (Hook. f.) Hedl. (3–6 pairs), S. kurzii (Watt ex Prain) C. K. Schneid (3–6 pairs) and S. macallisteri Rushforth (1–2 pairs) (Hedlund 1901; Hooker 1878; Koehne 1913; Prain 1904; Rushforth 1991; Schneider 1906) (Fig. 4 and Table 1). Sorbus gongshanensis is easily distinguished from all others by several distinctive characteristics (Long 1987; Lu and Spongberg 2003; Watson and Manandhar 2012) (Table 1). The red fruits distinguish S. gongshanensis from all species except S. kurzii. However, S. gongshanensis differs in its serrate leaflet margins toothed in the distal half or often almost to their base, the hypanthium reddish brown villous or glabrous and infructescences reddish brown villous. In all other species (exclude S. gongshanensis and S. kurzii), the fruits are typically white. Sorbus gongshanensis is also distinguished from S. macallisteri, S. helenae, and S. insignis by its persistent herbaceous stipules when fruiting (Table 1). Furthermore, S. gongshanensis have 2–4 pairs of leaflets which have serrate margins. Sorbus macallisteri only has 1–2 pairs of leaflets with few teeth. Sorbus helenae and S. insignis both have more pairs of leaflets (3–6 pairs) with the leaflets also longer and broader (10–20 cm long, 1.7–4 cm wide) than S. gongshanensis (Table 1).

Figure 4. 

Type materials of four similar species distinguishing Sorbus gongshanensis A Sorbus kurzii (G barcode 00437217) B Sorbus macallisteri (BM barcode 000602118) C Sorbus helenae (A barcode 00046019) D Sorbus insignis (K barcode 000758177).

Comparison of characters distinguishing Sorbus gongshanensis and similar species.

Sorbus gongshanensis S. kurzii S. macallisteri S. helenae S. insignis
Leaf & petiole length (cm) 8–10 & 1.5–2.5 7–11 & 1.2–2.8 3.5–6 & 1–1.8 13–20 & 2.5–4 10–15 & 1.7–3
Pairs of leaflets 2–4 3–6 1–2 3–4 3–6
Leaflet size (cm) 2.8–3.5 × 1–1.5 1.8–3.2 × 0.8–1.8 1.7–3 × 0.7–1.4 5–9 × 2–3 3–5 × 1–2
Margins Deep toothed 1/2 way and often almost to base Finely toothed in upper 1/2 Few teeth Serrate or doubly serrate Finely toothed in upper 1/2 or 1/4
Veins Glabrous Glabrous Glabrous Reddish brown villous along veins Glabrous
Stipules Herbaceous, semiorbicular, persistent Herbaceous, lanceolate, persistent Membranous, lanceolate, caducous Membranous, lanceolate, caducous Membranous, lanceolate, caducous
Inflorescences Reddish brown villous Reddish brown villous Glabrous Reddish brown villous Slightly pubescent
Hypanthium Reddish brown villous to glabrous Glabrous to pubescent Glabrous Glabrous Glabrous to pubescent
Infructescences Reddish brown villous Glabrous Glabrous Glabrous to pubescent Glabrous
Fruits color Red Red White White White

There are also several species sometimes with few pairs of leaflets found in other geographic regions. They are S. gracilis (Siebold et Zucc.) K. Koch [3–6 pairs of leaflets, distributed in Japan (Honshu, Shikoku, and Kyushu)], S. sargentiana Koehne (3–5 pairs of leaflets, distributed in southwest Sichuan Province, and northeast Yunnan Province), S. sambucifolia (Chamisso & Schlechtendal) M. Roemer (3–5 pairs of leaflets, distributed in Alaska, Japan, and the Russian Far East), and S. sitchensis M. Roem. (3–5 pairs of leaflets, distributed in the Pacific Northwest) (Chamisso and Schlechtendal 1827; Koch 1853; Koehne 1913; Roemer 1847; Siebold and Zuccarini 1846). Sorbus sargentiana, S. sambucifolia, and S. sitchensis have larger infructescences when fruiting (more than 30 fruits), while S. gracilis has large stipules (1.5 × 1.5 cm) at the nodes of the inflorescences. Sorbus gongshanensis can be easily distinguished from these four species by its few fruits and small stipule size.

Acknowledgments

The authors thank curators and staff at A, BM, CAS, CDBI, G, GH, K, KUN and NF for providing access to the herbarium material in their care. Our special thanks go to Anthony R. Brach and Kanchi N. Gandhi for help and suggestions, and to David E. Boufford, Danny Schissler and Steven Sylvester for linguistic help. This study was partially supported by grants from National Natural Science Foundation of China (Grant No. 31670192) to Xin-Fen Gao, and by the 2016 Shiu-Ying Hu Student/Post-Doctoral Exchange Award from Arnold Arboretum of Harvard University and NJFU Scientific Research Starting Foundation (Grant No. GXL2018039) to Meng Li.

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