Hanceola is a genus of eight herbaceous species previously thought to be endemic to southern China. However, H. suffruticosa, a new species described here from China and Vietnam, differs from all other species of Hanceola by its subshrubby habit. It is also distinct in its shallowly bicrenate laminae and densely purplish glandular puberulent inflorescences. The morphological description, illustrations, and distribution of the new species are presented. A key to all species of Hanceola is also provided.

Hanceola, Hanceolinae, new species, Ocimeae, Sino-Vietnamese border

Comprising about eight species, the genus Hanceola Kudô (Ocimeae, Nepetoideae, Lamiaceae) is endemic to the evergreen and mixed forests in southern China (Wu and Li 1977; Li and Hedge 1994; Harley et al. 2004). It can be distinguished from other genera of Ocimeae based on the following set of characters: cymes pedunculate and bracteolate, calyx 2-lipped (3/2, a 3-toothed posterior lip with median tooth larger, and a 2-toothed anterior lip), corolla 2-lipped (2/3, 2 lobes on the posterior lip and 3 lobes on the anterior) with tube clearly dilating at midpoint, and free filaments inserted near the throat of corolla (Wu and Li 1977; Li and Hedge 1994; Paton and Ryding 1998; Harley et al. 2004).

Hemsley established the genus Hancea Hemsl. with type species H. sinensis Hemsl. based on two syntypes, Faber 666 and 681, both collected from Mt. Omei of Sichuan Province (Forbes and Hemsley 1890). Considering that Hancea Hemsl. was a late homonym of Hancea Seem. (Euphorbiaceae), Kudô (1929) proposed a new name Hanceola Kudô for Hancea Hemsl.. Tribe Hanceoleae was proposed by Wu and Li (1977) in subfamily Ocimoideae sensu Briquet (1895–1897) to accommodate the distinct genus. Based on morphological cladistic analysis, Cantino (1992a, b) assigned all taxa of Ocimoideae to Nepetoideae sensu Cantino et al. (1992) and recognized Ocimoideae as tribe Ocimeae of subfamily Nepetoideae. Cantino et al. (1992) also placed the genus Siphocranion Kudô as a synonym under Hanceola. Since Siphocranion is distinct from Hanceola in its sessile and single-flowered cymes, Paton and Ryding (1998) resurrected Siphocranion from Hanceola, and treated the two genera as incertae sedis in Ocimeae together with Isodon (Schrad. ex Benth.) Spach. Harley et al. (2003) later established the subtribe Hanceolinae in Ocimeae to accommodate the three genera, which is adopted in the recent classification of Lamiaceae (Harley et al. 2004).

Zhong et al. (2010) first elucidated the phylogenetic relationships within Ocimeae based on molecular phylogenetic analyses. Using the nuclear ribosomal internal transcribed spacer (nrITS) and two plastid DNA regions (rps16 and trnL-trnF), they demonstrated that each of the three genera Siphocranion, Hanceola, and Isodon formed a distinct lineage within Ocimeae; the subtribes Siphocranioninae and Isodoninae were thus described to accommodate Siphocranion and Isodon, respectively (Zhong et al. 2010), while subtribe Hanceolinae is restricted to include Hanceola alone. Their results and treatment were further supported by Chen et al. (2019).

During our recent field investigations in Malipo County of Yunnan Province, southwestern China, an unusual species of Hanceola was discovered at the Sino-Vietnamese border. Further morphological studies suggested that it represents an undescribed species. Hereafter, we describe it as Hanceola suffruticosa Y.P. Chen, A.J. Paton & C.L. Xiang.

This study was based on comparison of herbarium specimens of Hanceola from 13 public herbaria AU, E, FJSI, HHBG, IBK, IBSC, LBG, K, KUN, NAS, PE, SM, and SZ (herbarium acronyms follow Index Herbariorum; Thiers 2020) and our new collections in China (herbarium specimens kept in KUN). Meanwhile, protologues of all published names and other related taxonomic literature (Forbes and Hemsley 1890; Kudô 1929; Sun 1942; Wu and Li 1977; Li and Hedge 1994; Paton and Ryding 1998; Harley et al. 2004) were collated and reviewed. Terminology for the description of the new species followed that of Li and Hedge (1994) and Harley et al. (2004).

Hanceola can be distinguished from all other genera of tribe Ocimeae by its pedunculate and bracteolate cymes, 2-lipped (3/2) calyx, 2-lipped (2/3) corolla abruptly dilating toward apex, as well as free filaments inserted near the throat of corolla (Wu and Li 1977; Li and Hedge 1994; Paton and Ryding 1998; Harley et al. 2004). Characterized by all these features, the new species we found at the Sino-Vietnamese border is shown to be a member of Hanceola. However, unlike other species of Hanceola, which are all perennial herbs, H. suffruticosa are subshrubs with woody and robust stems. In addition, the new species is distinct in its morphology of laminae and indumentum of branchlets and inflorescences. Specifically, laminae of most Hanceola species are lanceolate with base decurrent on petiole and margin coarsely dentate, whereas that of H. suffruticosa are oblong, ovate to ovate-lanceolate, with base not decurrent on petiole and margin shallowly bicrenate. Moreover, H. suffruticosa are purplish puberulent all over the branchlets and purplish glandular puberulent all over the inflorescences, while branchlets and inflorescences of other species of Hanceola are either subglabrous or with whitish glandular or eglandular hairs.

With all other species of Hanceola being endemic to southern China, H. suffruticosa is now the only species of the genera to be reported from China and Vietnam (Fig. 3). However, consistent with the habitat of other species, H. suffruticosa is also accustomed to the shady and moist evergreen mixed forests.

Though only nine species have been reported from Hanceola, most of them are only known from several old specimens. More efforts are needed to further reveal the relationships within these species. Here we provide a key to the nine species of Hanceola below.

We would like to thank Ms. Li-Qiong Jiang of Kunming Institute of Botany (KIB), Chinese Academy of Sciences for her assistance in field collection. Thanks are also extended to the staff of following herbaria for their valuable help in research facilities: E, IBSC, K, KUN, NAS, PE, and SZ. This work was supported by the CAS “Light of West China” Program to YPC and CLX, the National Natural Science Foundation of China (Grant no. 31670197), the Special Funds for the Young Scholars of Taxonomy of the Chinese Academy of Sciences (Grant no. ZSBR-006), the “Ten Thousand Talents Program of Yunnan” (YNWR-QNBJ-2018-279), and the “Excellent Young Scholars Program of Yunnan” (2019FI009) granted to CLX.