Ligularia monocephala, a remarkable new species from Hubei, China, is described and illustrated. It is readily distinguishable in the whole genus by character combination of the reniform to cordate-reniform leaf blades which are palmately-pinnately veined and abaxially purplish red, the solitary and erect capitula, and the pappus which are as long as or slightly longer than tube of the tubular corolla. A detailed description and distribution map of the species are also presented herein.

Compositae, Hubei, Shennongjia, taxonomy

Ligularia Cass., as the largest genus of tribe Senecioneae in Asteraceae in China, consists of approximately 130 species distributed mainly in eastern Asia (Liu 1989; Liu et al. 1994; Nordenstam 2007; Nordenstam et al. 2009; Liu and Illarionova 2011; Guo and Wang 2021). Since the publication of Flora of China (Liu and Illarionova 2011), the updated English version of Florae Reipublicae Popularis Sinicae (Liu 1989), extensive works have been done to the taxonomy of this genus at specific level (Fei et al. 2019; Lazkov and Sennikov 2019; Guo and Wang 2021, and references therein).

During a field expedition in August 2016 to Shennongjia, Hubei, China, the second author was able to discover a unique Ligularia population in an alpine region of this area. The plant, at first sight, shows an affinity with Ligularia hookeri (C.B. Clarke) Hand.-Mazz. in habit, however, the leaf color and the capitula orientation can easily set them apart. An in-depth survey of herbarium specimens was conducted, resulting in the finding of four gatherings (Anonymous 662, D.G. Zhang 080826018, Z.E. Zhao 1609 and X.L. Yu et al. 080078) all made from Shennongjia, Hubei, China, that are morphologically in conformity with this plant. To precisely decide the identity of these gatherings, we conducted another two field investigations to Shennongjia in September, 2020 and August, 2021, respectively, leading to a better understanding of the variation range of several main morphological characters of this plant. Upon careful observations and comparisons, it was found to be quite different from any other species in the genus in an array of morphological characters. We therefore concluded that this plant represents a hitherto undescribed species, which we describe below.

For morphological comparisons, we critically examined physical or digitalized herbarium specimens with high-resolution of the genus Ligularia at A, BM, CDBI, CSFI, E, GH, HIB, HITBC, HNWP, IBSC, JIU, K, KATH, KUN, LE, NAS, NY, P, PE, S, SZ, W, WU, and WUK (acronyms follow Thiers (2021)). Specimens were collected from Hubei (first in September 2020, second in August 2021) during our several field expeditions. The morphological measurements in the description are based on the in-situ observations and dried specimens deposited at IBSC and KUN. Its records of distribution, habitat and phenology are based on both field investigations and specimen records.

The generic placement of this newly described taxon, which is superficially similar to some species of Cremanthodium in the general habit (the gatherings Anonymous 662, D.G. Zhang 080826018, and Z.E. Zhao 1609 were, in fact, previously identified on the determination slips as species of Cremanthodium), is worthy of detailed remarks. The independent generic status of Cremanthodium, the putatively closest ally of Ligularia, has been widely accepted in recent checklists or Floras at the national level (e.g. Mathur 1995; Liu 1989; Grierson and Springate 2001; Kress et al. 2003; Liu and Illarionova 2011). Morphologically, the former is generally considered different from the latter by its broadly campanulate or hemispheric (vs. cylindrical or obconic) involucre, although this character is not always applicative in a few species (for example, C. liangshanicum L. Wang, C. Ren & Q.E. Yang). Geographically, the former is a high-alpine genus endemic to Sino-Himalayan region with its distribution range locating at 25°–40°N, 75°–104°E (Liu et al. 2002; Wang 2018), while the latter is an Eurasian genus more widely distributed than the former (Liu et al. 1994; Liu et al. 2002). However, the recognition and segregation of Cremanthodium has also been repeatedly questioned. It was once considered as an alpine variant (Wulff 1944) or ecotype (Drury 1967) of Ligularia. In addition, recent molecular phylogenetic studies focused on the LCP complex (Ligularia-Cremanthodium-Parasenecio; Asteraceae, Senecioneae) (Liu et al. 2006; Ren 2012; Ren et al. 2017, 2020) revealed that the two genera are not monophyletic as traditionally defined. They together form three distinct and distantly related clades on chloroplast gene trees, with two clades having the species of the two genera interspersed between each other. The results contradict heavily with Liu’s infrageneric classification system (Liu 1982, 1985) of the two genera established based mainly on morphological characters, but seem to be well correlated with the geographical distributions. Based on the above discussion, the newly reported species, characterizing by having cylindrical involucre, and locating at 31°N, 110°E, is here tentatively placed within Ligularia on morphological and geographical grounds.

In the genus Ligularia, L. monocephala is tentatively assigned to L. sect. Corymbosae (Franch.) Hand.-Mazz. ser. Retusae S.W. Liu due to its palmate-pinnate leaf venation, lanceolate to subulate bract, and cylindrical involucre. Within this series, it resembles L. phoenicochaeta (Franch.) Hand.-Mazz. to some extent, but differs mainly by the abaxially purplish red (vs. pale green) leaf blades (Fig. 2C), the erect (vs. cernuous) capitula (Fig. 2E), the cylindrical (vs. hemispheric) involucres (Fig. 2E), and the 5–7 mm (1–2 mm) long pappus (Fig. 2I). Ligularia monocephala is also superficially similar to L. jamesii (Hemsl.) Kom. of sect. Ligularia ser. Monocephalae (Nakai) Kitam. and L. hookeri (C.B. Clarke) Hand.-Mazz. (those plants with solitary capitula) of sect. Ligularia ser. Ligularia, particularly in the general habit and the solitary capitula. Morphologically, L. monocephala differs from L. jamesii immediately by the reniform to cordate-reniform (vs. triangular-hastate) leaf blades which are abaxially purplish red (vs. pale green, rarely purplish red) and apically rounded or slightly obtuse (vs. acute or acuminate) (Fig. 2C), the cylindrical (vs. broadly campanulate) involucres (Fig. 2E), the oblong to elliptic (vs. linear-lanceolate) ray laminae which are 6–7 mm (vs. 3–4 mm) wide (Fig. 2H), and the pappus which are as long as or slightly longer than tube of tubular corolla (vs. as long as tubular corolla) (Fig. 2I); and L. monocephala differs from L. hookeri mainly by the abaxially purplish red (vs. pale green, rarely purplish red) leaf blades (Fig. 2C), the erect (vs. cernuous to horizontal) capitula (Fig. 2E), the oblong to elliptic (vs. linear) ray laminae which are 6–7 mm (vs. 1.5–2 mm) wide (Fig. 2H), and the pappus which are as long as, or slightly longer than, the tube of tubular corolla (vs. as long as tubular corolla) (Fig. 2I). A detailed comparison of the four species is given in Table 1.

We would like to thank Dr. Chen Ren and Dr. Alexander Sennikov for their constructive suggestions. We are grateful to the curators of A, BM, CDBI, CSFI, E, GH, HIB, HITBC, HNWP, IBSC, JIU, K, KATH, KUN, LE, NAS, NY, P, PE, S, SZ, W, WU, and WUK for allowing us to use their scanned images of specimens and for research facilities. Thanks are also given to Mr. Xin-Qiang Guo, and Mr. Hai-Song Wu for field assistance. This work was supported by the National Natural Science Foundation of China (grant no. 31900183), the Biological Resources Programme of the Chinese Academy of Sciences (grant no. KFJ-BRP-017-08), Key Laboratory of Conservation Biology of Golden monkey in Shennongjia of Hubei Province (grant no. SNJGKL202002), the Youth Innovation Promotion Association of Chinese Academy of Sciences (grant no. 2019382), and the Ten Thousand Talents Program of Yunnan Province (grant no. 202005AB160005).