﻿Asterquanzhouensis (Asteraceae), a new riparian species from eastern China

﻿Abstract Asterquanzhouensissp. nov. (Asteraceae) from Fujian, eastern China, is described and illustrated. It grows on rocks in the riparian zone. Morphological, cytological and molecular investigations of A.quanzhouensis were carried out. The morphological data and phylogenetic analysis based on combined ITS, ETS and trnL-F dataset suggest that A.quanzhouensis is a separate species closely related to A.tonglingensis. The new species differs from the latter by the shorter stem length, leaf morphology, colour of phyllaries, number of ray florets, and achene shape. The cytological observation shows that the new species is diploid with a karyotype of 2n = 18.


Introduction
The genus Aster L. in its recent circumscription is restricted to Eurasia and comprises ~ 150 species, of which 123 occur in China ), a main diversity centre of Aster (Li et al. 2012). Recently, ten new Aster species have been described, and almost all these species have a narrow distribution pattern known from only one or two populations in different regions of China (Zhang et al. 2015(Zhang et al. , 2019Li et al. 2017Li et al. , 2020Xiao et al. 2019aXiao et al. , b, 2020Xiao et al. , 2021Xiong et al. 2019).
Recently, Guo-Jiao Yan, a young amateur naturalist and one of the authors of this paper, collected some unique samples from the riversides of the Min and Jin rivers, Quanzhou city, Fujian, eastern China. The morphological, cytological and phylogenetic data show that the specimens represent an undescribed species, which is reported herein.

Material collection
Specimens of the new taxon were collected in Dehua and Yongchun counties (Fig. 1), Fujian, China. We collected leaf material and dried it with silica gel for molecular experiments. The voucher specimens were deposited at the Herbarium of Hunan Normal University (HNNU) and Jiangxi Agricultural University (JXAU).

Morphological observations
The description of the new species is based on living material, dry specimens and FAAfixed materials. Twenty-one individuals were examined. The morphological comparison with Aster tonglingensis G.J.Zhang & T.G.Gao is based on the study of herbarium specimens, from PE, HNNU and JAXU. We compared the shape and size of the leaves, length of stems, phyllaries, number of florets, and achenes.

Cytology
Excised root tips from the cultivated plants of the new species were pretreated with 0.1% colchicine at 10 °C for 4 h, then fixed in Carnoy's solution (95% ethanol and glacial acetic acid in 3:1 ratio) at 20 °C for 12 h. The root tips were then macerated in 1 M hydrochloric acid at 60 °C for 10 min, stained in Carbol fuchsin solution, washed in distilled water for 30 min and finally depigmented and squashed in 45% acetic acid (Li et al. 2011). Karyotype formulae were calculated based on measurements of mitotic metaphase chromosomes taken from photographs. The symbols used to describe the karyotypes followed Levan et al. (1964).
Taxon sampling, DNA extraction, PCR reaction and sequencing Nuclear ribosomal DNA ITS and ETS sequences and plastid DNA trnL-F sequences of 66 species and varieties, representing major clades of the genus Aster and its relatives (Li et al. 2012(Li et al. , 2017Zhang et al. 2015Zhang et al. , 2019Xiao et al. 2019aXiao et al. , b, 2020Xiao et al. , 2021, were downloaded from GenBank (Appendix 1). Besides, eleven newly sequenced accessions are included from Dehua and Yongchun counties two individuals of Aster quanzhouensis (Appendix 1). The names of the taxa mentioned above follow Chen et al. (2011). Grangea maderaspatana (L.) Poir. and Dichrocephala integrifolia (L.f.) Kuntze were selected as outgroups following Li et al. (2012). Voucher specimens of newly sequenced material were deposited in HNNU. Total DNA extraction, PCR and sequencing were carried out according to Li et al. (2012).

Aster quanzhouensis
Phenology. Flowering from September to early December and fruiting from October to December.
Etymology. The species is named after its type locality, Quanzhou city, Fujian province, China.
Distribution and habitat. Aster quanzhouensis is known from Dehua and Yongchun counties, Quanzhou city, Fujian province, China. The new species grows on rocks in riparian habitats at an altitude of ca. 500 m a.s.l.
Conservation status. Aster quanzhouensis seems to be a narrowly distributed species, currently known only in rocky areas along two streams (Jin river and Min river) in Quanzhou city, and each population with ca. 150 (total < 1000) individuals were found. The habitat of A. quanzhouensis is easily disturbed or damaged. Further fieldwork is needed to evaluate the exact distribution of the species, and it is possible that other populations could be found in similar habitats of the Jin and Min rivers. Therefore, we only temporarily assign the species to the category DD (Data Deficient) according to the International Union for Conservation of Nature (IUCN 2022).

Cytology
The somatic chromosomes of the new species at metaphase are illustrated in Fig. 4. The two populations have a same karyotype formula, 2n = 18, and Stebbins' 1A-type (Stebbins 1971), but differs in ratio of long to short arm of chromosomes (the former is 1.02-1.55, while the latter 1.06-1.45), the chromosomes length (the former is 1.49-2.72, while the latter 1.71-2.77), and the AI value (the former is 0.54, while the latter 0.57).

Molecular phylogeny
The aligned lengths of ITS, ETS and trnL-F are 647 bp, 568 bp and 957 bp, respectively, yielding a concatenated alignment of 2172 bp. Character state changes were equally weighted and gaps were treated as missing data. ML and BI analyses produced similar topology and only the ML tree was presented in Fig. 5, with ML bootstrap (LP), and PP values for each clade. The phylogenetic results showed that the two samples of the new taxon were grouped together with strong support (PP = 1.00, LP = 100%) and are closely related to Aster tonglingensis with strong support (PP = 1.00, LP = 99%). According to these results, A. quanzhouensis is nested within the core Aster clade (PP = 1.00, LP = 100%) that is the redefined genus Aster in Eurasia (Li et al. 2012;Nesom 2020a, b).

Discussion
Morphological observations showed that Aster quanzhouensis has a perennial life form, lanceolate stigmatic appendage of disc florets, compressed fruits with two-or threeribbed and uniseriate pappus (Figs 2, 3). All Aster species share these characters. In the phylogenetic tree (Fig. 5), A. quanzhouensis is deeply nested within the core Aster (Li et al. 2012). Morphological and phylogenetic analyses support that A. quanzhouensis is sister to A. tonglingensis. As mentioned above, the two species can be easily distinguished from each other (Figs 2, 3, Table 1). Narrowly lanceolate leaves are rare in Eurasian Aster and can be found only in a few species, such as A. huangpingensis W.P.Li & Z.Li, A. dolichophyllus Y.Ling and A. tonglingensis. Our phylogenetic analyses (Fig. 5) revealed that the species with narrowly lanceolate leaves are nested in unrelated lineages of the genus Aster and are probably the result of convergent evolution. It is noteworthy to mention that they are all distributed in the same habitats confined to riparian rocks Zhang et al. 2019;Li et al. 2020). The same leaf character may be related to their habitat. When the water level rises in some periods during the course of the year, these species were submerged and their narrowly lanceolate leaves may represent adaptation to water flowing in the rivers or streams.
Karyotype variation usually accompanies evolutionary divergence, a general phenomenon observed in plants and animals (Rieseberg 2001). Two populations of the Aster quanzhouensis were found with the same karyotype formula and Stebbins' type, with only slight differences in the karyotypic indexes, which might mean that A. quanzhouensis is a young species.
Aster quanzhouensis is known only from two populations (Dehua and Yongchun counties) restricted to Quanzhou, Fujian, China, while A. tonglingensis is restricted to Mt. Tongling Natural Reserve, Wencheng county, Zhejiang (Zhang et al. 2019). These two species occupy the same ecological conditions, but are geographically separated by a distance of 400 km.