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Research Article
Saxifraga viridiflora (Saxifragaceae), an unusual new species from Guangxi, China
expand article infoXin-Jian Zhang§, Quan-Sheng Fu§, Jun-Tong Chen§, Li-Juan Li|, Peng-Rui Luo§, Jing-Yi Peng#, Xian-Han Huang, Hang Sun, Tao Deng
‡ Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
§ University of Chinese Academy of Sciences, Beijing, China
| University of Chinese Academy of Sciences, Kunming, China
¶ Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China
# Jishou University, Jishou, China
Open Access

Abstract

Saxifraga viridiflora, a remarkable new species of the genus Saxifraga sect. Irregulares (Saxifragaceae) from Guangxi, is described and illustrated herein. This new species morphologically differs from all known S. sect. Irregulares taxa by its greenish petals, verruculose sepals, and thick leathery leaf blade abaxially scarlet with white spots.

Keywords

China, Guangxi, new species, Saxifragaceae, taxonomy

Introduction

Saxifraga Linnaeus, the largest genus of Saxifragaceae, comprises more than 440 species widely distributed throughout the Northern Hemisphere (Pan et al. 2001; Tkach et al. 2015a, b). Previous molecular phylogenetic studies suggested that Saxifraga is monophyletic, providing that S. sect. Micranthes (Haw.) D. Don is excluded (Soltis et al. 1996; Prieto et al. 2013; Deng et al. 2015; Tkach et al. 2015a, b). Recent molecular phylogenetic research covered at least 13 sections and 9 subsections within the genus (Tkach et al. 2015b). S. sect. Irregulares Haw., characterized by zygomorphic flowers with two elongated petals and stamens with club-shaped filaments (Tkach et al. 2015b), is the ancestral clade of Saxifraga first described by Haworth (Haworth 1803; Soltis et al. 2001; Zhang et al. 2015; Tkach et al. 2015b; Zhang et al. 2019b). This section currently comprises 16 species mainly distributed in East Asia (Magota et al. 2021).

China has a vast territory with a wide range of complex and diverse topographies and soils and covering several climate types, which contribute to the wealth of Chinese botanical diversity (Sun et al. 2017; Chen et al. 2018). Twelve species of Saxifraga sect. Irregulares are native to China, including the recently reported new species, S. daqiaoensis F.G.Wang & F.W.Xing (Wang et al. 2008), S. kegangii D.G.Zhang, Y.Meng & M.H.Zhang (Zhang et al. 2017), S. luoxiaoensis W.B.Liao, L.Wang & X.J.Zhang (Zhang et al. 2018), S. shennongii L.Wang, W.B.Liao & J.J.Zhang (Zhang et al. 2019a), and S. damingshanensis W.B.Liao, W.Y.Zhao & J.H.Jin (Zhao et al. 2019).

In 2021, we inadvertently found a peculiar plant photograph posted on Baidu Tieba (https://tieba.baidu.com/), one of the most used Chinese communication platforms, and immediately deemed it to be a new species of Saxifraga sect. Irregulares, as it possesses zygomorphic flowers with two elongated petals and stamens with club-shaped filaments, but its petals are greenish, which cannot be found in any existing species of Saxifraga sect. Irregulares. We contacted the author of this photograph, Mr. Luo Dexuan, for phenological and geographical information regarding this specimen, and conducted fieldwork for this undescribed specimen. Subsequent morphological comparisons supported the status of the taxon as a new species, and it is described herein.

Taxonomy treatment

Saxifraga viridiflora X.J.Zhang, T.Deng, J.T.Chen & H.Sun, sp. nov.

Figs 1, 2

Type

China. Guangxi: Guilin City, Yongfu County, Baishou Town, 109°46'58.99"E, 25°5'15.5"N, 586 m alt., 27 June 2021, X.J. Zhang, D.X. Luo Zhangxj98 (Holotype: KUN!; Isotypes: JIU!, SYS!).

Diagnosis

Saxifraga viridiflora is easily distinguished from any other species of Saxifraga sect. Irregulares by having greenish petals (vs. white petals). S. viridiflora morphologically resembles S. epiphylla and S. kegangii, but is distinct from the latter two in its leaf blade abaxially scarlet with white spots (vs. abaxially greenish/reddish with brown or yellow-green spots), and sepals with verruculose surface (vs. sepals without verruculose surface) (Table 1).

Figure 1. 

Saxifraga viridiflora X.J.Zhang, T.Deng, J.T.Chen & H.Sun, sp. nov. A flower, petals 5, greenish B fruit, capsule winged when mature C inflorescence D infructescence E pedicels glandular pubescent; sepals red, glabrous, abaxially white verruculose F adaxial leaf surface dark green, crisped villous G, J abaxial leaf surface scarlet, with white spotted, crisped villous H rhizomes crisped villous, petiole base unsheathed I petiole with crisped villous K, L plants and habitat.

Figure 2. 

Photograph of the holotype of Saxifraga viridiflora X.J.Zhang, T.Deng, J.T.Chen & H.Sun, sp. nov. (Zhangx98, KUN1519096).

Table 1.

Diagnostic characters of Saxifraga viridiflora and comparison with other related species of S. sect. Irregulares.

Characters S. viridiflora sp. nov. S. epiphylla S. kegangii
Foliar embryo absent present absent
Leaf shape reniform to orbicular ovate fan-shaped to orbicular
Leaf margin shallowly crenate to subentire undulate, thickly dentate entire or 8–10-crenate
Leaf texture thick leathery to fleshy leathery leathery
Abaxial surface of leaf blade scarlet, with white spotted gray-green to red, with brown or yellow-green spotted gray-green, with yellow-green spotted
Trichomes on leaf both surfaces crisped villous both surfaces glandular hispid adaxially glabrous, abaxially glabrous or sparsely hispid
Petals greenish white, the base of three smallest petal with yellow spot white, the base of three smallest petal with yellow spot
Sepals red, glabrous, abaxially white verruculose greenish, abaxially and marginally glandular hairy, without verruculose greenish, abaxially and marginally glandular hairy, without verruculose

Description

Perennial herbs, 12–30 cm tall. Stolons absent. Rhizomes rather short. Leaves all basal; petiole 5–12 cm long, crisped villous dark-purple (ca. 6 mm); leaf blade reniform, thick leathery, 2.5–4.0 cm long × 3.5–5.3 cm wide, base cordate, margin undulate, apex obtuse, both surfaces crisped villous dark-purple (5.0–9.0 mm long), adaxially greenish, abaxially purple or dark red, with white spots. Inflorescence paniculate, ca. 20 cm long. 5–10-flowered; branches 2.0–3.0 cm long, glandular pubescent, 1–2-flowered; pedicels slender, 1.0–2.0 cm long, glandular pubescent. Flowers zygomorphic; sepals 5, spreading to reflexed, narrowly ovate, 2.5–3.5 mm long × 1.5–2 mm wide, glabrous, abaxially red, with white verruculose, adaxially greenish, 3–5-veined, apex obtuse. Petals 5, greenish, margin entire, glabrous, apex acute; the three smallest lanceolate, 3.0–4.0 mm long × 1.0–1.2 mm wide, 3-veined; the two largest lanceolate oblong, 0.7–1.4 cm long × 1.0–1.2 mm wide, 3-veined. Stamens 10, 3.2–4.0 mm long. Ovary ovoid, 1.5–2.0 mm long, disc obscure; styles divergent ca. 1.0–1.8 mm long. Capsule beaks winged when mature, carpels 5–7 mm long × 3–4 mm wide. Seeds elliptic, the two sides slightly bent, ca. 0.6 mm long.

Etymology

The specific epithet refers to the flowers of this new species that are green throughout the flowering period, differing from those of all other known Saxifraga sect. Irregulares species. The Chinese name is given as “绿花虎耳草” (lǜ huā hǔ ěr cǎo), referring to the greenish petals of the new species.

Phenology

In a two year personal observation of this new species in its native range, Guangxi. Guilin City (Luo Dexuan, pers. comm.), S. viridiflora was flowering from April to July and fruiting from June to August.

Distribution and ecology

The new species, Saxifraga viridiflora, is currently known only from Yongfu County, Guangxi Province, China. It was observed to grow on dry limestone under dense jungles at altitudes between 500 and 600 m.

Paratypes

China. Guangxi. Guilin City, Yongfu County, Baishou Town, 109°46'49.3"E, 25°5'16.1"N, 547 m alt., 10 July 2021, X.J. Zhang, L.J. Li, J.Y. Peng, P.R. Luo Deng12030 (KUN); same locality, 575 m alt., 27 June 2021, X.J. Zhang, D.X. Luo Zhangxj99 (KUN).

Discussion

The new species Saxifraga viridiflora has zygomorphic flowers and stolons absent, which indicate a position in S. sect. Irregulares ser. Rufescentes. Saxifraga viridiflora is distinct from all known sect. Irregulares taxa by its greenish petals, verruculose sepals, and thick leathery leaf blade abaxially scarlet with white spots.

Geographically, Saxifraga viridiflora was only found in Yongfu County of Guangxi Province, China. It grows only on dry rocks under dense jungles in limestone area, whereas other related species of sect. Irregulares usually grow on damp cliffs and rocks nearby valleys. Here we argue that the environmental heterogeneity plays an important role in the differentiation of the species in sect. Irregulares, given the leaf blade of Saxifraga viridiflora is thick leathery or fleshy (grow on dry rocks), while the leaf blade of other related species of sect. Irregulares are mainly papery or leathery (grow on damp rocks).

Notably, only seven species of Saxifraga sect. Irregulares were recorded in “Flora of China” (Pan et al. 2001). However, six new species of S. sect. Irregulares were discovered in China in recent years, provided that Saxifraga viridiflora is counted. Furthermore, most of these new species were confined to a narrow geographical range. Species richness of S. sect. Irregulares has been quite underrated, and more field investigations and phylogenetic analyses are needed to infer its biodiversity and speciation history.

Since several new species of S. sect. Irregulares have been published in recent years, we include here an identification key to include all species known so far for this section.

Identification key to Saxifraga sect. Irregulares

1 Stolons arising from axils of basal leaves, filiform S. stolonifera
Stolons absent 2
2 Aerial stems developed; leaves cauligenous S. sendaica
Aerial stems not developed; leaves radical 3
3 Leaf blade abaxially spotted 4
Leaf blade abaxially usually concolorous 12
4 Leaf blade elliptic to oblong, base cuneate S. kwangsiensis
Leaf blade fan-shaped or ovate to broadly so, base cordate or peltate 5
5 Leaf blade with foliar embryos in sinus adaxially S. epiphylla
Leaf blade without foliar embryos 6
6 Leaf base peltate 7
Leaf base cordate 8
7 Leaf blade papyraceous, apex acute S. mengtzeana
Leaf blade thickly coriaceous, apex obtuse S. daqiaoensis
8 Leaf margin lobed 9
Leaf margin shallowly crenate to subentire 11
9 Capsule beaks winged; leaf lobes margin irregularly dentate S. luoxiaoensis
Capsule beaks divergent; leaf lobes margin entire 10
10 Abaxial surface of leaf blade purple spotted S. damingshanensis
Abaxial surface of leaf blade yellow spotted S. shennongii
11 Leaf blade abaxially gray-green with yellow-green spots S. kegangii
Leaf blade abaxially scarlet with white spots S. viridiflora
12 Longest petal serrate at margin S. fortunei
Longest petal entire at margin 13
13 Leaf cleft 14
Leaf shallowly lobed 15
14 Upper petals nearly lanceolate, not spotted S. acerifolia
Upper petals widely ovate, spotted S. cortusifolia
15 Bracts leafy S. nipponica
Bracts linear 16
16 Flowering stem and inflorescence reddish long glandular villous S. rufescens
Flowering stem and inflorescence shortly glandular pubescent S. imparilis

Acknowledgements

The authors are deeply grateful to Mr. Luo Dexuan, who first discovered this species, for offering kind assistance during the fieldwork. This study was supported by grants from the Biodiversity Survey and Assessment Project of the Ministry of Ecology and Environment, China (2019HJ2096001006), the Second Tibetan Plateau Scientific Expedition and Research (STEP) program (2019QZKK0502), the Key Projects of the Joint Fund of the National Natural Science Foundation of China (U1802232), the Youth Innovation Promotion Association of Chinese Academy of Sciences (2019382), the Young Academic and Technical Leader Raising Foundation of Yunnan Province (2019HB039).

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