﻿Sinosenecioyangii (Asteraceae), a new species from Guizhou, China

﻿Abstract A new species Sinosenecioyangii D.G. Zhang & Q. Zhou (Asteraceae, Senecioneae) from Guizhou Province, China, is described and illustrated based on its morphological characteristics and molecular evidence. It closely resembles S.confervifer and S.guangxiensis, the former in the scapigerous habit and smooth and glabrous achene surface, the latter in the calyculate involucre and purple abaxial leaf surface, and both in the shape and indumentum of leaf lamina, but differs markedly from the latter two in having fewer capitula and epappose achenes. Phylogenetic analysis based on nrITS and ndhC-trnV sequences shows that this new species belongs to the S.latouchei clade and is sister to S.guangxiensis with moderate support.


Introduction
Sinosenecio B. Nordenstam (1978) (Senecioneae, Asteraceae) contains 45 species mainly distributed in central and southwestern parts of China (Chen et al. 2011;Liu and Yang 2012;Liu et al. 2019;Zou et al. 2020;Chen et al. 2022). This genus is characterized by subscapiform or leafy stems, palmately or rarely pinnately veined leaf lamina, solitary to numerous capitula, and ecalyculate or sometimes calyculate involucres, etc. (Jeffrey and Chen 1984). Sinosenecio encompasses two species assemblages, i.e. the Sinosenecio s.s. group and the S. oldhamianus group, with different chromosome number (x = 30 vs. 24 or 13), patterns of endothecial cell wall thickenings (strictly polarized vs. polarized and radial), and phylogenetic affiliation (subtrib. Tussilagininae s.s. vs. subtrib. Thephroseridinae) (Liu 2010;Liu and Yang 2011a, b;Gong et al. 2016). These two groups also differ in geographical distribution. The former is restricted to mountainous regions around Sichuan Basin, southwestern China, and the latter is widely distributed in central and southern China, with two species extending to Indochina (Gong et al. 2016). However, a formal taxonomic adjustment is not yet proposed as phylogenetic relationships in subtrib. Thephroseridinae need to be further clarified (Nordenstam and Pelser 2011).
Libo County (Guizhou Province, China) belongs to the slope zone of transition from Guizhou Plateau to Guangxi Hilly Basin with typical karst topography and complex and diverse ecological environment (Tan 2010). In the past few years, some new species have been reported in this area, such as Strobilanthes hongii (Chen et al. 2019) and Petrocodon luteoflorus (Fan et al. 2020). During our field investigation at Lihua Town, Libo County in March 2021, we found several unusual Sinosenecio populations that morphologically resemble two members of the S. oldhamianus group, namely S. confervifer (H. Léveillé) Y. Liu & Q. E. Yang and S. guangxiensis C. Jeffrey & Y. L. Chen, but differs markedly from them in several morphological features, respectively. After examining herbarium specimens and relevant literature, we verified that it represents an undescribed species. Here, we described it as S. yangii D. G. Zhang & Q. Zhou with report on its chromosome number and phylogenetic position.

Morphological observation
Morphological examination and comparison of the new species with S. confervifer and S. guangxiensis were based on fresh materials and herbarium specimens. Chromosome observation was conducted according to Meng et al. (2010).

Molecular analyses
To test the phylogenetic affiliation of S. yangii, we carried out phylogenetic analysis based on combined matrix of ITS and ndhC-trnV sequences. The matrix contained 23 accessions from 20 species, including the new species, 16 species of S. oldhamianus group, two of Nemosenecio, and an outgroup Tephroseris flammea (Turcz. ex DC.) Holub. The ITS and ndhC-trnV of S. yangii were sequenced in this study and the  Table 1. Sequences obtained were edited using Sequencher-5.4.5 and then combined by Sequence Matrix-1.9 (Vaidya et al. 2011). Multi-sequence alignment and manual adjustment were conducted using programme CLUSTAL_W in Mega-X64 (Rédei 2008) and gaps were treated as missing data. Phylogenetic trees were constructed using Bayesian Inference (BI) and Maximum Likelihood (ML) in CIPRES Portal (https://www.phylo.org/portal2). BI and ML analyses were performed using MrBayes version-3.2 (Ronquist et al. 2012) and RAxML-8.2.10 (Stamatakis 2014), respectively. For BI analysis, GTR+G was selected as best-fitting model using Akaike information criterion (AIC) in JmodelTest 2-2.1.6 (Posada 2008). The Markov chain Monte Carlo analyses were run with four simultaneous chains of 10,000,000 generations sampling one tree every 1,000 generations. After the first 25% of trees were discarded as burn-in, the remaining trees were used to construct a majority-rule consensus tree with Bayesian posterior probabilities. ML analysis was performed with GTRCAT model, support values was calculated with 1,000 bootstrap replicates using a fast bootstrapping algorithm (Stamatakis et al. 2008).

Morphology and taxonomy
Morphological observation ( Fig. 1) showed that S. yangii, S. confervifer, and S. guangxiensis share obvious resemblance in the leaf blade shallowly undulate and suborbicular, adaxially densely to sparsely villous and abaxially sparsely pubescent or nearly glabrous (Table 2). In addition, S. yangii is similar to S. confervifer in the stem leafless or with 1-2 bract-like leaf and smooth achene surface, and to S. guangxiensis in the calyculate involucre. Nevertheless, S. yangii differs from both species in having fewer capitula (usually 1-3) and epappose achenes. The metaphase chromosomes of this species were counted to be 2n = 48 ( Fig. 2A). The achene surface was glabrous and smooth ( Fig. 2B) and the anther endothecial cell wall thickenings were polarized and radial (Fig. 2C).

Phylogenetic analyses
The combined matrix of ITS and ndhC-trnV sequences contained 1,324 aligned bp. Bayesian (BI) and Maximum likelihood (ML) trees had similar topologies. The BI tree was presented in Fig. 3 with BI posterior probability (BP) and ML bootstrap support values (LP) labelled on the branches. Ingroups were resolved into two clades, viz. the S. latouchei clade (BP = 1, LP = 99) and the S. oldhamianus-Nemosenecio clade (BP = 1, LP = 99). Sinosenecio yangii was resolved as sister to S. guangxiensis (BP = 0.87, LP = 71) in the former clade, while S. confervifer was recovered as a member in the latter clade.

Discussion
Several lines of evidence demonstrated that S. yangii is a member of the S. oldhamianus group. Sinosenecio yangii has a base chromosome number of x = 24 ( Fig. 2A) and polarized and radial anther endothecial cell wall thickenings (Fig. 2C), which are typical of the S. oldhaminanus group. Analyses of ITS and ndhC-trnV sequences also corroborated its phylogenetic affiliation, resolving it as sister to S. guangxiensis in the S. latouchei clade of S. oldhaminanus group. Sinosenecio yangii was morphologically and phylogenetically close to S. guangxiensis in the S. latouchei clade. However, there are differences in morphology, distribution and ecology between the two species. S. yangii is easily distinguished from S. guangxiensis in the stem leafless or with 1-2 bract-like leaf (vs. 1-5 cauline leaves), fewer capitula (vs. 2-7 or more), smooth and glabrous achene surface (vs. papillate and pubescent), and epappose achenes (vs. present pappus). From the perspective of distribution area, the former is restricted to Libo County in Guizhou, appearing on the wet rock cliff, and the geographical location is adjacent to the border with Guangxi province. The latter is distributed in the Guangxi and southwestern Hunan, growing on the damp, shady places or rocky places at mountain summits. To some extent, the close relationship between these two species may also be related to their distributional ranges adjacent to each other. Additionally, it is worth noting that the epappose achenes of S. yangii is a character previously never recorded in the S. latouchei clade. Description. Scapigerous herbs. Rhizomes short and stout with many fibrous roots. Stems slender, scapiform, erect or declining, solitary or several, 13-22 cm long, basally reddish-brown and sparsely white villous, almost smooth in upper part. Radical leaves several; petiole ca. 3-6.5 cm long, densely villous or glabrescent, basally expanded, not auriculate; lamina suborbicular or reniform, ca. 2.5-4.5 × 2.5-6.5 cm, base cordate, margin irregularly triangular dentate, shallowly undulate or entire, apex slightly acute; adaxially green, densely or sparsely pubescent, abaxially pale green or purplish red, sparsely arachnoid or nearly glabrous. Upper leaves 1 or 2, bract-like, shortly petiolate, lanceolate. Capitula usually 1-3, peduncles slender, ca. 2-3.5 cm long, with a basal linear bracteole, or with 1-2 small linear bracteoles in the upper part. Involucres campanulate, calyculate with 2-3 bracteoles or more; phyllaries ca. 13, lanceolate, ca. 6 mm long, with ciliate margin, apically acute or obtuse and sometimes purplish. Ray florets ca. 13, corolla tube 3 mm long, glabrous; ray yellow, oblong, ca. 12 mm long, 4-veined, apically 3-denticulate. Disc florets numerous; corolla yellow, 4 mm, with ca. 1.5 mm glabrous tube and 0.85 mm limb. Anthers oblong, 5, ca. 1.2 mm long, basally obtuse. Style branches ca. 0.5 mm long, puberulent. Achenes ca. 1 mm long, smooth and glabrous. Pappus absent.

Sinosenecio yangii
Phenology. Flowering from March to May, fruiting from April to June. Etymology. The species was named after Professor Qin-er Yang, an expert in the field of Asteraceae at the Chinese Academy of Sciences. The Chinese name is given as " 亲二蒲儿根" (qīn èr pú ér gēn). Distribution and habitat. Sinosenecio yangii is known from Lihua Town, Libo County, Guizhou Province, China (Fig. 6). It was collected from a rock cliff by the side of a rural road in this town, at an altitude of 347 m.