Pedicularis multicaulis W.B.Yu, H.Wang & D.Z.Li (series Oliganthae Prain) is a new species described and illustrated herein. This new species is endemic to northwest Yunnan and only two populations were found in Weixi county. Phylogenetic analyses support P. multicaulis as a new species, sister to P. taihaiensis Bonati and P. macilenta Franch. Morphological comparisons between P. multicaulis and P. macilenta and P. taihaiensis also support P. multicaulis as a new species to science.

Orobanchaceae, Pedicularis multicaulis, Mountains of Southwest China, phylogenetic analysis

Pedicularis Linn., with around 600 species, is the largest genus of Orobanchaceae and widely distributed throughout the North temperate region (Fischer 2004, Stevens 2001, Yu et al. 2015). More than 350 species have been recognised in China (Yang et al. 1998). Of them, about two-thirds of the species are restricted in the Hengduan Mountains, which belongs to the Mountains of Southwest China hotspot (Wang 2006, Wang and Wu 1994). Due to the previously limited accessibility of the Mountains of Southwest China before the 21^st century, several new species of Pedicularis have subsequently been discovered and described in the 2000s, owing to the construction of a road system under China’s Great Western Development Strategy (Liu and Yu 2015, Yang et al. 2003, Yu et al. 2010, Yu et al. 2018).

According to the phylogeny of the Pedicularis species with well-represented samples from the Hengduan Mountains region, 18 taxa were not categorised as any recognised species, based on both molecular and morphological data (Yu et al. 2015), which could be potential new species or new records to China. Of them, two taxa had been described as new species, P. wanghongiae M.L.Liu & W.B.Yu (Liu and Yu 2015) and P. millina W.B.Yu, D.Z.Li & H.Wang (Yu et al. 2018). In this study, we described and illustrated another new species, P. multicaulis W.B.Yu, H.Wang & D.Z.Li, from the remaining 16 taxa after carefully examining morphological characters and in comparisons with herbarium specimens of the close relatives, P. taihaiensis Bonati and P. macilenta Franch. (Yu et al. 2015). Pedicularis multicaulis is strongly supported as a new species, based on the revised phylogenetic analyses. Meanwhile, the pollen morphology of P. multicaulis was investigated using a scanning electron microscope (SEM).

The fresh specimens of the new species were collected from Pantiange and Lidiping in Weixi county, northwest Yunnan, China. Pollen samples were collected from the type specimens, then observed under SEM (ZEISS EVO LS10, Germany). For the morphological comparisons, we examined specimens or specimen images of the closest relatives from the herbaria E, K, KUN, LA, P and PH. Selected type specimens of P. macilenta and P. taihaiensis are presented in Suppl. material 1: Figures S1 and S2.

According to the published phylogeny of Pedicularis (Yu et al. 2015), P. multicaulis, P. macilenta and P. taihaiensis were chosen as ingroups and P. cephalantha Franch. ex Maxim. and other species from series Oliganthae Prain, Strobilaceae Tsoong and Amplitubae Li were also included (Table 1). Pedicularis axillaris Franch. ex Maxim. was specified as the outgroup. In this study, we had two samples of the new species from Pantiange (W.-B. Yu et al. 2014102) and Lidiping (W.-B. Yu et al. 2014096), respectively, two samples of P. tahaiensis from Luquan (C.-L. Xiang et al. HP9544) and Huize (W.-B. Yu et al. HW10369), respectively and one sample of P. macilenta. Four DNA regions (nrITS, matK, rbcL and trnL-F) were used and the new sequences generated following Yu et al. (2011). Bayesian Inference (BI), Maximum Likelihood (ML) and Maximum Parsimony (MP) methods were used to reconstruct the phylogenies. The BI analysis was performed using MrBayes 3.26 (Ronquist and Huelsenbeck 2003). The total dataset was partitioned (see Suppl. material 2: Dataset 1) and the DNA substitution model of Bayesian Information Criterion (BIC) for four DNA regions was estimated using jModeltest 2 (Darriba et al. 2012). The ML analysis was conducted with RAxML 8.2.10 (Stamatakis et al. 2008). The MP analysis was carried out using PAUP* 4.a165 (Swofford 2003). Parameters for the three analyses followed the previous studies (Yu et al. 2013, Yu et al. 2015).

The conservation status of P. multicaulis was assessed in accordance with IUCN Red List Criteria (IUCN 2012).

The galea of P. multicaulis bears one pair of distinct reflexed marginal teeth on both sides, which is the key character of series Oliganthae Prain. Phylogenetic analyses did not support series Oliganthae as monophyletic (Yu et al. 2015). The previous study indicated that P. macilenta and P. taihaiensis formed a weakly supported clade, then sister to P. multicaulis (= Pedicularis sp. (9)) by using one sample of each species. In this study, both P. multicaulis and P. taihaiensis had two samples from different populations and our results showed that P. multicaulis and P. taihaiensis formed a strongly supported clade, then sister to P. macilenta. The relationship amongst the three species was well resolved. Therefore, population level sampling is very important for species delimitation and phylogeny of recently derived lineage.

Morphological characters differentiate P. multicaulis from the two most closely related species (Table 2). The key diagnostic characters of P. multicaulis are having taller and more branched stems, partially crawling stems with fibrous roots, shorter petiole of cauline leaves and smaller corollas with a short beak. The three species are also isolated geographically (Figure 5). According to herbarium records, P. taihaiensis occurs in Luquan and Huize, north Yunnan and P. multicaulis is only found in Weixi, northwest Yunnan. The distribution of P. macilenta is disjunct, with one population in Eryuan, northwest Yunnan and another in Zhaotong, northeast Yunnan. As all three species were mainly confined to the habitat of wet meadow, we assume that geographical isolation may play an important role in species divergence in this lineage.

We are grateful to Hui Tang and Xiu-Long Yang for their kind help in the field; to Zhen-Long Liang for the line drawing; to Ting Tang and Yin Zhao for preparing SEM investigation; and to the curators of the herbaria K, KUN, LA, P and PH for making specimens available for access in the herbarium or online database. This study was supported by grants from the Large-scale Scientific Facilities of the Chinese Academy of Sciences (2017-LSFGBOWS-02), Chinese Academy of Sciences Strategic Priority Research Program of the Chinese Academy of Sciences (XDB31000000) and the National Natural Science Foundation China (31470323, 31870196).