Youngiahangii (Asteraceae, Crepidinae), a new species from Hubei, China

Abstract Youngiahangii T.Deng, D.G.Zhang, Qun Liu & Z.M.Li, sp. nov., a new species of Asteraceae, is described and illustrated. It was collected in Wufeng County, Hubei Province, Eastern Central China. Youngiahangii is morphologically most similar to Y.rubida, but can be easily distinguished from the latter by capitula with 8–10 florets and the hairy leaf surface. Phylogenetic analyses, based on the internal transcribed spacers (ITS) and one chloroplast marker (rps16), showed that Y.hangii and Y.rubida were sister species with good support. The results of both phylogenetic analysis and the morphological data support the specific rank of Y.hangii.


Introduction
Youngia Cass. (Cassini 1831) (Asteraceae; Cichorieae) is an East Asian genus with about 32 species (Babcock and Stebbins 1937;Shih 1997;Shih and Kilian 2011; plants of Youngia from a cave in Wufeng County, Hubei (Fig. 4). After comparing them with the known species, we determined that they represent a new taxon, which we hereby describe as Y. hangii.

Morphological assessment
We compared the shape, lobes and size of the leaves, leaf surface, phyllaries, number of florets, achenes and pappus of the new collections with Y. rosthornii, Y. rubida and Y. heterophylla and with descriptions in literature, in the Herbarium of the Kunming Institute of Botany (KUN). Eight individuals of the new species were examined.

DNA Sequencing and Molecular Analyses
For molecular analysis, we sampled a sample from one population of the unknown species and obtained 38 samples from 26 related species from GenBank (Appendix 1). Voucher information and GenBank accession numbers are presented in Appendix 1. Total genomic DNA was extracted from dried leaves using a Plant Genomic DNA Kit DP305 (Beijing, China) and used as the template in the polymerase chain reaction (PCR). Two sequences (ITS and rps16) were combined by Sequence Matrix v.1.7.8 for later analysis (Vaidya et al. 2011). Multiple-sequence was aligned using the programme CLUSTAL_W v.1.4 (Rédei 2008), followed by manual adjustment in Bi-oEdit v.7.0.5.3 (Hall 1999). Gaps were treated as missing data.

Taxonomic treatment
Distribution and habitat. Youngia hangii is known only from the type locality, Renheping in Wufeng Xian, Hubei, China; 500-1000 individuals are known along the edge of some small caves at the base of the karst hillside ( Fig. 2A, B, C); at altitudes of 500-800 m.
Morphological assessment. Morphological characteristics suggest that Y. hangii is related to Y. rubida and Y. heterophylla owning 10-25 florets and resembles Y. rosthornii with bipinnately deeply partite leaves. The achenes of Y. hangii and Y. rubida are attenuated into a short beak, which is widened into the pappus disc. Several unique features including the shape, lobes and size of the leaves, the leaves with white simple hairs (Fig. 2E, F, G; Fig. 3F, G), phyllaries, number of florets and achenes differentiate Y. hangii from Y. rubida and Y. heterophylla (Table 1).
Phylogenetic analysis. The Bayesian tree showing PP support, ML bootstrap (LP) and MP bootstrap (BP) values for each clade are presented in Fig. 1. The species in clade Ι form a monophyletic group with PP = 0.97, but LP are with weak support and BP are in conflict with PP and they were instead with "-", respectively in Fig. 1. Youngia hangii is nested within Clade I as sister to Y. rubida with strong support (PP = 1, LP = 83, BP = 88).

Discussion
Owning only 8-10 florets supports a placement of Youngia hangii in Y. sect. Youngia and its small involucres and achenes further support that Y. hangii is related to Y. rubida. However, there are some obvious differences between Y. hangii and Y. rubida and other species in the shape, lobes and size of the leaves and in white pubescent surfaces of the leaves. Moreover, Y. rosthornii also has bipinnately deeply partite leaves, but its leaves with a large apical part are different from Y. hangii.
Based on the combined datasets of the ITS and rps16 sequences, BI, MP and ML trees with similar topologies were constructed. Youngia hangii was clustered with Y. rubida and nested in Y. sect. Youngia with strong support (PP = 1, LP = 87, BP = 74) and was sister to the clade of Y. rubida with strong support (PP = 1, LP = 83, BP = 88). The results from the phylogenetic analysis are consistent with the morphological comparisons. Although only one sample of Y. hangii was included in the phylogenetic analysis, Y. hangii and Y. rubida have obvious differences in morphology, so the morphological data and phylogenetic results altogether support our hypothesis of Y. hangii being a new species.