Synotis baoshanensis (Asteraceae), a new species from Yunnan, China

Description

Herbs, shrub-like, or subshrubs, 50–150 cm tall. Stems erect, branching, slender, glabrous. Leaves short-petiolate; petiole 1–1.5 cm long, glabrous, exauriculate; blade narrowly elliptic or oblong-elliptic, 5–22 cm long, 2–5 cm broad, base narrowly cuneate, margin prominently mucronate-serrate, apex acute-acuminate, papery, both surfaces glabrous, pinnately veined, lateral veins 12–18, arcuate-ascending, somewhat prominent abaxially; uppermost and branch leaves obviously smaller. Capitula radiate, numerous in lax axillary and terminal rounded compound corymbs; peduncles 2–3 mm long, densely pubescent, bracts and/or bracteoles 1 or 2. Involucres cylindrical, 5–5.5 mm long, 1.5–2 mm broad, calyculate; bracts of calyculus 2 or 3, ca. 1 mm long; phyllaries 5, oblong-linear, 5–5.5 mm long, 1–1.5 mm broad, margin scarious and subglabrous, apex obtuse and pubescent, often purplish. Ray florets 2 or 3; corolla ca. 8 mm long; tube ca. 4 mm long; lamina yellow, oblong, 3.5–4.5 mm long, ca. 1 mm broad, 3-denticulate, 2- or 3-veined. Disk florets 2 or 3; corolla yellow, 6–7 mm long, tube 3 mm long, infundibuliform limb exserted, narrow; lobes ovate-oblong, ca. 2 mm long, apex acute. Anthers ca. 3 mm long; anther tails 1/4 –1 3/4 as long as anther collar; appendages ovate; anther collars distinctly dilated at base. Style arms 1–1.2 mm long, fringed with short papillae, central tuft prominent, much longer than laterals. Achenes cylindrical, ca. 1.5 mm long, sparsely pubescent. Pappus white, ca. 5 mm long.

Etymology

The specific epithet ‘baoshanensis’ is derived from the type locality, Baoshan City, southwestern Yunnan Province, China.

Phenology

Flowering October–November; fruiting December.

Distribution and habitat

Synotis baoshanensis is currently known only from Baihua Ling, Longyang District, Baoshan City, southwestern Yunnan Province, China (Figure 3). It grows in shady, mixed forests between 2,350 and 2,550 m above sea level.

Floral micromorphological characters

As shown in Figure 4A, the anther collar of Synotis baoshanensis is balusterform, being basally dilated and consisting of larger cells, conforming to the results reported previously for some other species of Synotis (Jeffrey and Chen 1984; Tang et al. 2013). The anther endothecial cell wall thickenings were distributed along all the inner walls, and thus were radial (Figure 4B). The findings agree with previous reports for other species of Synotis (Jeffrey and Chen 1984; Tang et al. 2013). The placement of Synotis in subtribe Senecioninae as defined by Nordenstam (2007) is corroborated by the results.

Chromosome cytology

The metaphase chromosomes were determined to be 2n = 40 (Figure 5A). The karyotype analysis was performed on the basis of five well-spread metaphase cells. The chromosomes ranged in length from 4.0 to 6.7 μm, and total karyotype length was 107.0 μm. According to the chromosome nomenclature of Levan et al. (1964), S. baoshanensis had 20 median-centromeric (m), 14 submedian-centromeric (sm), and 6 subterminal-centromeric (st) chromosomes (Figure 5B), i.e. 2n = 40 = 20m + 14sm + 6st. The chromosomes showed a steady gradation in length from the longest to the shortest, with no evidence of bimodality.

As pointed out by Tang et al. (2013), Synotis is poorly known cytologically. In addition to the chromosome number of S. baoshanensis here counted, chromosome numbers for only six species have been reported (Mehra et al. 1965; Mehra and Remanandan 1975; Gupta and Gill 1981, 1989; Liu et al. 2006; Gupta et al. 2010; Tang et al. 2013; this study). Synotis baoshanensis, S. changiana Y. L. Chen and S. xinningesis M. Tang & Q. E. Yang are the only species in the genus for which the karyotype has been analyzed (Tang et al. 2013; this study). In chromosome number and chromosome morphology, the three species are very similar to each other, although in gross morphology S. baoshanensis is remarkably different from S. xinningesis and S. changiana, with S. baoshanensis belonging to ser. Microglossae C. Jeffrey & Y. L. Chen under sect. Synotis (see below); the latter two species belong to ser. Synotis, indicating that the Synotis may be karyologically rather constant.

Notes

Synotis baoshanensis is most similar to S. auriculata (Figure 1B) in leaf shape and in the number of phyllaries and florets, but differs by the glabrous stem and petiole (vs. glandular pubescent) (Figure 6), the exauriculate petiole (vs. auriculate) (Figure 6), the uppermost leaves obviously smaller than the middle ones (vs. almost equally sized), and the larger ray florets (4–4.5 mm vs. ca. 2.5 mm).

As shown in Figure 3, Synotis baoshanensis is distributed in southwestern Yunnan, China, while S. auriculata is in southern Xizang (Tibet), China, so the two species are geographically isolated. Both species prefer similar habitats, growing in mixed forests at elevations between 2,000 and 2,600 m above sea level.

Five Synotis species closely related to each other and all endemic to Assam, India, i.e., S. borii (Raizada) R. Mathur, S. jowaiensis (Balak.) R. Mathur, S. lushaensis (C. E. C. Fisher) C. Jeffrey & Y. L. Chen, S. rhabdos (C. B. Clarke) C. Jeffrey & Y. L. Chen, S. simonsii (C. B. Clarke) C. Jeffrey & Y. L. Chen (Jeffrey and Chen 1984; Mathur, 1986), are somewhat similar to S. baoshanensis in habit, inflorescence shape, and pappus color, but all these Assam endemics are readily distinguishable from S. baoshanensis by, among others, the more or less broadly elliptic or oblong-elliptic leaves. In addition, Synotis phupeakensis H. Koyama, a species from northeastern Thailand (Koyama 1988) and also similar to S. baoshanensis in habit, inflorescence shape, and pappus color, is remarkably distinct by the large auricules at base of petiole, the campanulate involucres with 10 phyllaries, the ray florets 5, and the disk florets 7 or 8.

In leaf characters Synotis baoshanensis is somewhat reminiscent of S. acuminata (Wall. ex DC.) C. Jeffrey & Y. L. Chen, a species widely distributed in the eastern Himalayan region. Both species have narrowly elliptic or oblong-elliptic leaves, with the petiole not auriculate. However, Synotis baoshanensis is different from S. acuminata in the inflorescences round-topped (vs. flat-topped), the phyllaries 5 (vs. 3 or 4), the ray florets 2 or 3 (vs. 1) and oblong (vs. linear), and the pappus white (vs. stramineous). In fact, these two species should be classified under different series if following the infrageneric division proposed by Jeffrey and Chen (1984), and Chen (1999) (see below).

Jeffrey and Chen (1984), and Chen (1999) divided Synotis into two well-marked sections, sect. Synotis and sect. Atractylidifoliae C. Jeffrey & Y. L. Chen; all but one of the species (S. atractylidifolia) fall within the former, which itself is divisible into five not very clearly differentiated series. Synotis baoshanensis is characterized by leafy stems, round-topped inflorescences, white pappus, and 5 or 6-flowered, minutely radiate capitula, and thus can be readily referred to ser. Microglossae C. Jeffrey & Y. L. Chen, whereas Jeffrey and Chen (1984), and Chen (1999) have placed S. acuminata in ser. Fulvipapposae C. Jeffrey & Y. L. Chen, a series featuring, among others, flat-topped inflorescences and stramineous pappus. In China, ser. Microglossae now includes five species, namely S. auriculata, S. baoshanensis, S. glomerata (J. F. Jeffrey) C. Jeffrey & Y. L. Chen, S. saluenensis (Diels) C. Jeffrey & Y. L. Chen, and S. triligulata (Buch.-Ham. ex D. Don) C. Jeffrey & Y. L. Chen (Chen et al. 2011; this study), of which S. baoshanensis has the largest ray florets. The five species mentioned above can be distinguished by features in the following key.