Schnabelia jiuzhaigouensis C. Liu, F. Zhao & C.L. Xiang, a new species from north-eastern Sichuan, China, is described, based on both morphological and molecular phylogenetic evidence. Morphologically, the new species is mostly similar to S. terniflora, but can be readily distinguished by its habit, ovate to lanceolate-ovate leaf blades, the presence of 5–8 lateral veins on each side of the mid-rib and distinct characteristics of the floral structure, including oblong upper lip and lateral lobes of the lower lip, with the middle lobe being cuneate. In addition, the nutlets are puberulent and lack reticulate venation. Molecular phylogenetic analyses place the new species at a basal position within the genus Schnabelia. The new species is categorised as Data Deficient (DD) according to the IUCN Red List Categories and Criteria. A key to all species of Schnabelia is also provided.

Ajugeae, morphology, new species, Schnabelia, taxonomy

Schnabelia Hand.-Mazz. (Lamiaceae, Ajugoideae) is a small genus endemic to China. The genus was first described by Handel-Mazzetti (1921), based on specimens collected from Hunan Province in central China. The taxonomic placement and circumscription of Schnabelia have long been debated. Initially, in the traditional taxonomic treatment (Handel-Mazzetti 1921; Chen 1977; Chen and Gilbert 1994), the genus was placed within Verbenaceae, containing only two species (S. oligophylla Hand.-Mazz. and S. tetrodonta (Y.Z.Sun) C.Y.Wu & C.Chen), both characterised by 4-winged stems. However, based on the character of the deeply-lobed ovaries, P’ei (1932) transferred Schnabelia to the family Lamiaceae, associating it with Ajuga L. and Teucrium L., a classification supported by P’ei and Chen (1977). Cladistic analysis using morphological data by Cantino et al. (1999) revealed that the traditionally defined Caryopteris Bunge was not monophyletic and led to the transfer of three species of Caryopteris (i.e. C. aureoglandulosa (Vaniot) C.Y.Wu, C. nepetifolia (Benth.) Maxim. and C. terniflora Maxim) to Schnabelia. Subsequent molecular phylogenetic analyses (Huang 2002; Shi et al. 2003) further confirmed that at least the latter two species are closely related to S. oligophylla.

Recently, based on broad sampling and comprehensive evidence from morphological and molecular data, Xiang et al. (2018) reconstructed the backbone phylogeny of Ajugoideae. Their analyses confirmed the findings of Cantino et al. (1999), supporting the non-monophyly of the traditional circumscribed Caryopteris and monophyly of the re-defined Schnabelia. Furthermore, Xiang et al. (2018) divided Schnabelia into two sections. Sect. Schnabelia consists of two species (S. oligophylla and S. tetrodonta), characterised by perennial herb, 4-winged stems, caducous leaves and nutlets puberulent. In contrast, sect. Cylindricaulis C.L.Xiang & H.Peng includes three species (S. aureoglandulosa, S. nepetifolia and S. terniflora), characterised by subshrubs, nearly terete stems without wings, persistent leaves and densely hirsute nutlets with distinct reticulate venation.

As an endemic genus, all species of Schnabelia are distributed across central, northern, southern and south-western China, primarily inhabiting the slopes of mountains within subtropic forests (Wu and Li 1977; Xiang et al. 2018; Wang 2019; Zhao et al. 2021; Wang and Hong 2022). During a field expedition in Sichuan Province in 2019, we discovered an intriguing species of Schnabelia. Through comparative morphological studies and molecular phylogenetic analyses using plastid and nuclear DNA sequences, we determined this species as a new species of the genus Schnabelia and describe and illustrate it here.

A total of 14 DNA sequences were newly generated in this study, including the seven DNA regions from two accessions of the potential new species. The combined plastid dataset had an aligned length of 4,689 bp (1,136 bp for matK, 1,258 bp for rbcL, 839 bp for trnL-trnF, 1008 bp for rps16 and 448 bp for trnH-psbA), while the combined nuclear dataset was 992 bp (532 bp for ITS, 460 bp for ETS), respectively.

The phylogenetic topologies from Maximum Likelihood (ML) and Bayesian Inference (BI) analyses were congruent, so only the ML trees were provided for discussion (Figs 1, 2). Both analyses strongly supported the monophyly of Schnabelia (ML-BS = 100%, BI-PP = 1.00; all values follow this order hereafter), with the genus Rubiteucris found to be sister to Schnabelia (100%/1.00). The phylogenetic tree constructed in this study is largely consistent with previous studies, based on the plastid DNA (Li et al. 2016; Xiang et al. 2018; Zhao et al. 2021).

Figure 1. 

Phylogenetic relationship of Schnabelia, based on the (5CPDNA) dataset. The support values (BS/PP) indicated at branches. BS values < 50% and PP support < 90% indicated by -. The outgroup and recognised groups are marked in the right bar.

Figure 2. 

Phylogenetic relationship of Schnabelia, based on the (2NR) dataset. The support values (BS/PP) indicated at branches. BS values < 50% and PP support < 90% indicated by -. The outgroup and recognised groups are marked in the right bar.

Within Schnabelia, the two accessions of the new species formed a clade (Fig. 1: 100/1.00; Fig. 2: 100/1.00). In the plastid phylogenetic tree, the two individuals of the new species formed a subclade sister to the remaining five species and relationships amongst these species were consistent with previous studies (Xiang et al. 2018). In addition, each species formed a monophyletic subclade (Fig. 1).

However, the nuclear phylogenetic tree revealed three subclades. The first subclade included two accessions of the new species and three individuals of Schnabelia oligophylla, forming a moderately supported subclade (Fig. 2. 73/0.94). The second subclade consisted of two individuals of S. tetrodonta (Fig. 2. BS/PP = 69/-), while the third subclade (BS/PP = 99/1.00) consisted of the remaining three species (S. nepetifolia, S. aureoglandulosa and S. terniflora). The relationship amongst species within this subclade were consistent with those found in the plastid phylogenetic tree.

Morphologically, based on its non-winged stem and persistent leaves, the potential new species should be placed within sect. Cylindricaulis. It is most similar to Schnabelia terniflora, but can be distinguished by differences in habit, leaf characteristics, corolla shape and the surface ornamentation of the nutlets. Detailed morphological differences between the two species are summarised in Table 2.

Taxonomic treatment

 Schnabelia jiuzhaigouensis C.Liu, F.Zhao & C.L.Xiang, sp. nov.

urn:lsid:ipni.org:names:77357312-1

Fig. 3

Type.

China • Sichuan Province, Jiuzhaigou County, in the vicinity of Wujiao Ranger Station of Wujiao Nature Reserve, the wet area along the stream, under the mixed forest, 32°54′42″N, 104°14′38″E, 2599 m a.s.l., 12 July 2019, flowering, Ting Zhang, C. Liu, H. Jiang, Y.L. He & C.H. Li 19CS18246 (holotype: KUN 1630399!), (isotype: KUN 1630400!; CDBI0290980!)

Figure 3. 

Morphology of Schnabelia jiuzhaigouensis. A, B habitat C leaf morphology D frontal view of inflorescence E lateral view of inflorescence F lateral view of flowers and filaments (Scale bar: 5 mm) G frontal view of calyces (Scale bar: 1 mm) H surface of the nutlets. (Scale bars: 1 mm) (Photo by Cheng Liu).

Diagnosis.

Schnabelia jiuzhaigouensis is most similar to S. terniflora, but can be distinguished by several morphological differences. Schnabelia jiuzhaigouensis is a perennial herb (vs. shrub), with ovate to lanceolate-ovate leaf blades, 2–8 × 1.5–4 cm (vs. lanceolate-oblong to ovate, 1.5–4 × 1–3 cm in S. terniflora), the lateral veins on each side of the mid-rib number 5–8 (vs. 3–6 in S. terniflora).The upper lip and lateral lobes of the lower lip are oblong in S. jiuzhaigouensis (vs. broadly obovate in S. terniflora) and the middle lobe is cuneate (vs. subrounded). The corolla is puberulent on the outside, but non-glandular (vs. puberulent and glandular in S. terniflora) and the nutlets puberulent (vs. densely hirsute), with S. jiuzhaigouensis lacking reticulate veins on the nutlets (vs. with distinctly reticulate veins in S. terniflora). The differences between the new species and S. terniflora are summarised in Table 2.

Description.

Perennial herbs, erect, 20–60 cm tall. Stems 4-angled and puberulent, occasionally branched from base; internodes 1–11 cm long, puberulent. Leaves opposite, petiole 0.3–2.5 cm long, puberulent; leaf blades ovate to lanceolate-ovate, papery, 2–8 × 1.5–4 cm, puberulent on both surfaces, hairs denser along veins abaxially, base broadly cuneate to rounded or subcordate, apex acuminate, margin serrate, lateral veins 5–8 on each side of the mid-rib. Inflorescences axillary cymes, 1–3 flowered; peduncle slender, (0.5)1.5–3.5 cm, puberulent; pedicels 0.2–1 cm long; bracts lanceolate, ca. 1–2 mm long, glabrous or sparsely hairy, bracteoles lanceolate, 0.5–1 mm long. Calyx campanulate, 10-veined, outside sparsely pubescent; tube 1–1.5 mm long, lobes 5, lanceolate, ca. 2–3 × 1 mm, margin entire, apex acuminate. Corolla pink, 2-lipped, outside sparsely puberulent; tube ca. 5 mm long, both surfaces puberulent; upper lip 2-lobed, lobes oblong, ca. 3–3.5 × 1 mm; lower lip 3-lobed, lateral lobes oblong, ca. 2.5–3 × 1 mm, middle lobe larger, cuneate, 5–6 × 3–4 mm. Stamens and style strongly exserted; stamens 4, inserted near corolla throat, filaments 6–8 mm, basally hairy; style 13–16 mm, glabrous, apex subequally 2-lobed. Ovary pubescent. Nutlets 4, ovoid, puberulent, ca. 3 × 2 mm, without reticulate veins.

Phenology.

Flowering from June to July, fruiting from July to September.

Distribution and habitat.

Currently, S. jiuzhaigouensis is known from two locations in Wujiao Xiang, Jiuzhaigou County, Sichuan, China. It grows under the forest together with species of Picea brachytyla (Franch.) E.Pritz. (Pinaceae), Rosa omeiensis Rolfe (Rosaceae), Impatiens undulata Y.L. Chen & Y.Q. Lu (Balsaminaceae) and Mimulus L., at elevations from 2500 m to 2600 m.

Etymology.

The specific epithet ‘jiuzhaigouensis’ is derived from the type locality Jiuzhaigou County.

Chinese name.

Jiǔ Zhài Gōu Sì Léng Căo (Chinese pronunciation); 九寨沟四棱草 (Chinese name).

Conservation status.

So far, two small populations of Schnabelia jiuzhaigouensis have been observed in the Wujiao Nature Reserve. These populations are geographically close enough to be considered part of a single location. Further detailed investigation of the same habitats is necessary to gain a better understanding of the species’ distribution, abundance and potential threats. Therefore, this species is currently classified as Data Deficient (DD) according to the IUCN Red List Categories and Criteria (IUCN 2024).

Additional specimens examined.

Schnabelia jiuzhaigouensis (paratypes). China • Sichuan: Jiuzhaigou County, Jiawuchi scenic spot of Wujiao Xiang, under the forest with the species of Picea brachytyla, 32°58′29″N, 104°09′29″E, 2551 m a.s.l., 15 July 2019, flowering, Ting Zhang, C. Liu, H. Jiang, Y.L. He & C.H. Li 19CS18370 (KUN!).

Specimens of S. terniflora examined.

China, Gansu • Kang County, Qujiagou, 09 Aug 2011, W. Fang et al. fw11146 (KUN), Jia’an Town, Yuanjiawan, 01 May 1963, Y.Q. He & C.L. Tang 145 (WUK) • Tanchang County, Hanban County, 11 Jul 1951, T.P. Wang 14296 (PE) • Wen County, Motianling, Baishui Jiang Nature Reserve, 07 May 2007, D.E. Boufford et al. 37468 (PE), Bikou Town, Yinchanggou, 05 Jul 1964, Q.X. Li & X.C. Zhao 2037 (NWTC), Fanba Town, Heiyinggou, 19 Aug 1976, J.X. Yang 3730 (IBSC); Zhouqu County, Gongbagou, 16 Jul 1998, Baishuijiang Exped. 064 (PE); Hubei • Shennongjia, on the way from Xinhua to Xiaoluoxi, 11 Jun 2013, C.L. Xiang et al. 749 (KUN); Shaanxi • Mian County, Fangjiaba, 12 Apr 1942, K.T. Fu 3529 (PE), Liushuying, 15 Apr 1938, T.P. Wang 9065 (WUK); Nanzheng County, Near Xiaoba Village, 21 Apr 1973, X.X. Hou 496 (WUK); Near Xiaotai Mountain, 07 May 1956, Huanghe Exped. 521 (WUK); Sichuan • Dujiangyan City, Shichangwan, 19 Apr 1952, Z. He 12165 (PE), Erwang Temple, 27 Apr 1987, D.Z. Fu et al. 87-0276 (WCSBG), Qingcheng Mountain, 14 Apr 1930, F.T. Wang 20395 (WUK), Yulei Mountain. 23 Aug 1987, Z.Y. Li et al. 87-1962 (WCSBG); Maerkang County, 11 May 1957, X. Li 70613 (IBSC), Shuadan Road, 17 May 1957, X. Li 70662 (NAS) • Mao County, Fushun Town, Gangou, 1 Aug 1975, Sichuan Veget. Exped. 8680 (CDBI) • Nanping (Jiuzhaigou) County; 26 Oct 1937, T.P. Wang 7974 (PE), 17 May 1979, Anonymous 0098 (SM) • LangZhai Village, 15 Jul 1983, Sichuan Veget. Exped. 30420 (CDBI).

The authors are indebted to the curators of the Herbaria BM, CDBI, IBK, IBSC, K, KUN, NAS, NWTC, PE, SM, SZ, WCSBG and WUK for their assistance in research facilities. The authors also thank the anonymous reviewers for their helpful comments and feedback, which greatly improved the quality of our manuscript.