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Sedum ichangensis, a new species of Crassulaceae from Hubei, China
expand article infoYu-Bing Wang, Xing-Jun Xiong§
‡ China Three Gorges University, Yichang, China
§ Changyang Hospital of Traditional Chinese Medicine, Changyang, China
Open Access

Abstract

Sedum ichangensis sp. nov., from Yichang, Hubei province, central China, is described and illustrated. The new species is similar to S. elatinoides and S. rosthornianum in its leaf and carpel morphology and differs in its creeping stems and solitary flowers. The conservation status of S. ichangensis was assessed as Endangered according to the IUCN Red List criteria.

Keywords

Crassulaceae, Flora of China, Flora of Hubei, new species, Sedum sect. Filipes

Introduction

Sedum Linnaeus (1753: 430), the largest genus in the family Crassulaceae with about 430 species, is particularly diverse in East Asia, the Mediterranean and North America (Linnaeus 1753; ’t Hart and Bleij 2003; Thiede and Eggli 2007). Sedum can easily be distinguished by its usually alternate leaves, sessile carpels with slightly connate at the base, separate, mostly yellow or white petals and stamens with two whorls (Thiede and Eggli 2007); however, molecular studies have revealed that Sedum is a highly polyphyletic group (Nikulin et al. 2016) which may be due to the high morphological plasticity and variability within the genus (Carrillo-Reyes et al. 2009). In China, 121 species were recorded in the "Flora of China" (Fu and Ohba 2001). Since 2001, six new species have been described, namely S. hoi X. F. Jin & B. Y. Ding (2005: 381), S. spiralifolium D.Q. Wang, D.M. Xie & L Q. Huang (2014: 117), S. plumbizincicola X.H. Guo & S.B. Zhou ex L.H. Wu (2013: 492), S. fanjingshanensis C. D. Yang & X. Y. Wang (2012: 389), S. kuntsunianum X. F. Jin, S. H. Jin & B. Y. Ding (2013: 34) and S. peltatum M. L. Chen & X. H. Cao (2017: 847).

According to the recent taxonomic treatment of Fu and Ohba (2001), the species of Sedum in China are divided into three sections, viz. Sedum sect. Sedum, sect. Oreades (Fröderström) K.T. Fu and sect. Filipes (Fröderström) K.T. Fu. The section Sedum is distinct from both sections Oreades and Filipes in its adaxially gibbous carpels and follicles (vs. carpels and follicles not gibbous); while the sect. Oreades differs from the sect. Filipes in its spurred (vs. spurless) leaf base and petals that are mainly yellow (vs. mainly white or reddish-purple) (Fu and Ohba 2001).

An unknown Sedum species, belonging to the sect. Filipes, was discovered in Hubei Province, Central China. The species is described as new to science in this study.

Material and methods

Three scattered populations of an unknown Sedum species were discovered in Yichang city of Hubei Province, Central China in 2014. These populations were continuously observed over 2 years. Fresh specimens collected from these populations were morphologically studied and illustrated. The distribution map was constructed with Arcgis 10.2, using data provided on the specimen labels.

Specimens of the morphologically similar species Sedum elatinoides Franchet (1883: 11) and S. rosthornianum Diels (1900: 361) were collected from Hubei province for comparison. Specimens of Sedum sect. Filipes deposited at PE, HIB, WH and CCAU were largely checked, based on the relevant literature (Fu and Ohba 2001, Fu 2001). Furthermore, digital images of type specimens archived at the JSTOR Global Plants website (http://plants.jstor.org) were examined.

Taxonomy

Sedum ichangensis Y. B. Wang, sp. nov.

Figures 1, 2

Diagnosis

Sedum ichangensis has papillate carpels and appears to be morphologically similar to S. elatinoides and S. rosthornianum. It can be distinguished from S. elatinoides by its perennial habit (vs. annual) and solitary flower (vs. flowers in cymes) and from S. rosthornianum in its entire leaf margins (vs. leaf margins dentate), its branched stems (vs. stems simple) and its solitary flowers (vs. flowers in paniculiform cymes). (Table 1, Fig. 1, 2).

Morphological comparison between Sedum ichangensis and related species.

Item Sedum ichangensis Sedum elatinoides Sedum rosthornianum
Habit perennial annual perennial
Stem prostrate erect erect
Phyllotaxis 4–6-verticillate 3–6-verticillate opposite or 3- or 4-verticillate
Leaf blade narrowly ellipsoid, entire narrowly oblanceolate, entire rhombic-oblong, dentate
Inflorescence solitary flower paniculiform or corymbiform cyme paniculiform cyme
Petal white, pinkish toward the apex white white
Figure 1. 

Sedum ichangensis Y. B. Wang from type locality A habitat B flowering stems C flower D unripe follicles E carpels with style.

Figure 2. 

Sedum ichangensis Y. B. Wang, sp. nov. A habit B flower C carpels D single carpel.

Type

CHINA: Hubei Province, Yichang city, Changyang County, Longzhouping Town, on rocks, alt. 130 m. 30°28'N, 111°11'E, 19 Jul 2017, ycmy032 (holotype, CTGU!; isotypes HIB!, and PE!).

Description

Perennial herbs. Roots fibrous. Stems procumbent, divaricately branched, 1–2 mm in diameter, up to 35 cm long, with scattered reddish dots. Leaves 4–6-verticillate, entire, sessile, narrowly ellipsoid, 5–12 × 1.5–2.5 mm, base attenuate, apex acute. Flowers 5-merous, solitary in the axils of upper leaves, 5–8 mm in diameter. Pedicel 1.5–2.5 cm long. Sepals 5, lanceolate, 1.5–2 mm long, apex acute. Petals 5, white, pinkish towards the apex, lanceolate, 4–5 × 1–2 mm, apex acute. Stamens 10, in 2 whorls, slightly shorter than the petals, antesepalous ones ca. 4 mm long, antepetalous ones ca. 3 mm long, inserted ca. 1 mm above the petal base, filaments white, 1.6–2.4 mm long, anthers ca. 0.4 mm long, reddish. Nectar scales spatulate, ca. 0.4 mm long. Carpels 5, white, suberect, adaxially minutely papillate, broadly ovoid, ca. 2 mm long, base united for ca. 0.2 mm, styles ca. 1.5 mm long. Follicles divergent, 0.8–1.1 mm long, with scattered reddish dots, seeds numerous, brown, ca. 0.5–1 mm long, papillate.

Phenology

Flowering from early May to July, fruiting from August to October.

Distribution and habitat

Sedum ichangensis is known from Longzhouping town of Changyang County, Gufu town of Xingshan County and Muyang River of Yiling County in Yichang City of western Hubei Province, central China (Fig. 3). It grows on rocks of roadsides, especially in fissures filled with soil, at an elevation of ca. 100–280 m.

Figure 3. 

Distribution of Sedum ichangensis in Hubei province, central China. The three known localities are indicated with triangles.

Chinese name

Yi-chang-jing-tian (宜昌景天).

Etymology

The specific epithet of this new species is dedicated to the Yichang city.

Taxonomic notes

Sedum ichangensis belongs to Sedum sect. Filipes on account of its carpels adaxially not gibbous, its spurless leaf base and its white flowers (Fu and Ohba 2001). Sedum ichangensis is a species easily identifiable by its floral, stem and leaf features. The new species resembles S. elatinoides in the leaf characters, as well as the structure of the flowers. However, S. ichangensis differs from S. elatinoides in its perennial habit with branched stems and its solitary flowers. Sedum ichangensis differs from S. rosthornianum in its much branched, decumbent stems, entire leaf margins and its solitary flowers. Here, we provide photographs (Fig. 1), line drawings (Fig. 2) and a detailed morphological comparison (Table 1), as well as a key to the species of Sedum sect. Filipes in China to facilitate its identification.

Additional specimens examined (paratypes)

CHINA. Hubei Province: Xingshan County, Gufu town, 200 m alt., 31°20'N, 110°45'E, 15 May 2017, YB Wang ycmy022 (CTGU), same loc. XJ Xiong XXJ024 (CTGU); Yiling County, Muyang River, 280 m alt., 30°44'N, 111°02'E, 3 August 2017, YB Wang ycmy139 (CTGU).

Conservation status

Based on field investigations, S. ichangensis occurs only in three scattered areas. The total area of occupancy is less than 500 km2; each population possesses no more than 300 mature individuals. It prefers habitats on rocks along roads. Human activities are impairing its populations severely. The type population, which grew close to a road, was seriously impacted in its survival due to herbicide spraying in 2018. Based on currently available information, the conservation status of this species is categorised as Endangered [EN] following the IUCN Categories and Criteria (IUCN 2017).

Key to the species of Sedum sect. Filipes in China (adapted from Fu and Ohba 2001)

1 Plants perennial, fasciculate; stamens in 1 series S. correptum
Plants annual or biennial, rarely perennial, solitary or tufted; stamens in 2 series 2
2 Plants glandular hairy 3
Plants glabrous. 4
3 Plants annual; stems soft; leaves 2–4 × 1.4–2.5 cm S. drymarioides
Plants biennial; stems ± woody at base; leaves 0.7–1.5 × 0.7–0.9 cm S. stellariifolium
4 Carpels minutely papillate 5
Carpels smooth 7
5 Stems simple, erect; leaf margin dentate S. rosthornianum
Stems many branched, decumbent; leaf margin entire 6
6 Plants annual; stems erect, flowers in cymes S. elatinoides
Plants perennial, stems creeping, flowers solitary S. ichangensis
7 Carpels 3 S. bonnieri
Carpels 5 8
8 Petals reddish-purple; flowering stems branched, ca. 20 cm S. filipes
Petals white; flowering stems simple, ca. 10 cm S. majus

Acknowledgements

We would like to thank Associate Professor Qiao Li for her excellent illustrations of S. ichangensis. Thanks are also due to the reviewers for their useful suggestions. This study was supported by the Special funds for science and technology innovation of Hubei (grant no. 2018ACA132).

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