The indumentum of nutlets is shown to be of phylogenetic importance in previous molecular phylogenetic studies of Paraphlomis, a genus of Lamiaceae with approximately 30 species distributed mainly in southern China and Southeast Asia. Nearly half the species of Paraphlomis are known from limestone areas. In this study, we described and illustrated a new species, P. hsiwenii, from the karst mountain forests in Guangxi Zhuang Autonomous Region, China. Our molecular phylogenetic analyses revealed that P. hsiwenii is recovered in a clade consisting of species with hairy nutlets. The new species is morphologically most similar to P. pagantha from the same clade, but they differ in the morphology of lamina bases, length of pedicels and calyces, as well as the morphology of upper corolla lips.

Ajugoides, karst, Matsumurella, nutlet, Paraphlomideae

In a recently updated phylogenetic and taxonomic study of Lamioideae, the tribe Paraphlomideae was established to accommodate three genera, Ajugoides Makino, Matsumurella Makino, and Paraphlomis (Prain) Prain (Bendiksby et al. 2011). Ajugoides is a monotypic genus endemic to Japan and Matsumurella comprises five species distributed in East Asia (Harley et al. 2004; Bendiksby et al. 2011). As the largest genus of Paraphlomideae, Paraphlomis consists of ca. 30 species occurring mainly in China (especially in the south of the Yangtze River) and Southeast Asia (Wu and Li 1977; Li and Hedge 1994; Harley et al. 2004; Chen et al. 2021).

Morphologically, Paraphlomis can be distinguished by its herbaceous habit with stoloniferous stems and simple hairs, two to many-flowered verticillasters, actinomorphic and tubular to obconical calyces, 2-lipped (1/3) corollas, and apically truncate ovaries (Wu and Li 1977; Li and Hedge 1994; Harley et al. 2004; Chen et al. 2021). Two sections and five series were recognized in a previous infrageneric classification of Paraphlomis from China, divided based on the shape of calyx (tubular or obconical) and calyx teeth (e.g., conspicuous or inconspicuous, broadly triangular or subulate) (Li 1965; Wu and Li 1977). However, the most recent molecular phylogenetic study of Paraphlomis indicated that nutlet morphology (e.g., glabrous or hairy, obviously inflated or not) rather than the above-mentioned calyx characters is of phylogenetic value for the subdivision of the genus.

Species of Paraphlomis are mostly accustomed to shady and moist places in tropical and subtropical evergreen and mixed forests, and nearly half of the species are karst-adapted (Wu and Li 1977; Li and Hedge 1994; Zhang et al. 2020; Chen et al. 2022a). During our recent field investigations in the limestone area of Diding Natural Reserve in Guangxi Zhuang Autonomous Region, China, we found a putative new species of Paraphlomis which is characterized by hairy nutlets. We further confirmed its specific status as a new species and placement within the genus based on molecular phylogenetic and morphological evidence, and named it P. hsiwenii Y.P.Chen & XiongLi.

A total of 15 sequences (i.e., the five DNA regions of the two accessions of P. hsiwenii and one accession of P. pagantha) were newly generated in the present study. The aligned length of the combined nuclear data set and combined plastid data set was 1251 bp (808 bp for ITS, 443 bp for ETS) and 2479 bp (850 bp for rpl32-trnL, 812 bp for rps16, 817 bp for trnL-trnF), respectively. The topologies of the BI and ML trees were largely consistent with each other, but the BI trees are slightly better resolved. Thus, only the Bayesian 50% majority-rule consensus trees of the two combined data sets are presented, the posterior probabilities (PP) and Bootstrap support (BS) values being superimposed on the nodes (Figs 1, 2).

Figure 1. 

Bayesian 50% majority-rule consensus tree of Paraphlomis based on combined nuclear (ITS and ETS) data set. Support values ≥ 0.50 PP or 50% BS are displayed above the branches (an “*” indicates a support value = 1.00 PP or 100% BS and a “-” indicates a support value < 50% BS). Multiple accessions of the same species are numbered according to Appendix 1.

Figure 2. 

Bayesian 50% majority-rule consensus tree of Paraphlomis based on combined plastid (rpl32-trnL, rps16, and trnL-trnF) data set. Support values ≥ 0.50 PP or 50% BS are displayed above the branches (an “*” indicates a support value = 1.00 PP or 100% BS). Multiple accessions of the same species are numbered according to Appendix 1.

Both the nuclear and plastid data sets recovered species of Matsumurella within the Paraphlomis clade (Fig. 1: PP = 1.00/BS = 100%; Fig. 2: PP = 1.00/BS = 98%), indicating that neither of the two genera is monophyletic. As for relationships within the Paraphlomis-Matsumurella clade, some deep nodes in the nuclear tree (Fig. 1) and most shallow nodes in the plastid tree (Fig. 2) are poorly resolved, and topological conflicts between the two trees can be immediately recognized, especially at the placements of P. javanica var. pteropoda D. Fang & K.J. Yan, P. albiflora (Hemsl.) Hand.-Mazz., and P. nana Y.P. Chen, C. Xiong & C.L. Xiang. The backbone topologies of Paraphlomis recovered in the present study are largely consistent with those of previous studies (Chen et al. 2021, 2022a, b), and the intergeneric relationships within Paraphlomideae and phylogenetic relationships within Paraphlomis have been discussed in Chen et al. (2021). Therefore, our following discussion will focus on the placement of the new species.

The two accessions of P. hsiwenii group together and form a strongly supported clade (Fig. 1: PP = 1.00/BS = 100%; Fig. 2: PP = 1.00/BS = 100%). In the plastid tree, relationships between P. hsiwenii and other species of Paraphlomis are not resolved (Fig. 2). In the nuclear tree, the new species is sister to P. jiangyongensis X.L. Yu & A. Liu but with weak support values (Fig. 1: PP = 0.66/BS = 54%). The two species are further placed within a robustly supported clade (Fig. 1: PP = 1.00/BS = 91%) together with P. albida Hand.-Mazz., P. gracilis (Hemsl.) Kudô, P. kwangtungensis C.Y. Wu & H.W. Li, P. pagantha, and Matsumurella yangsoensis (Y.Z. Sun) Bendiksby. This clade is corresponding to “Clade III” in Chen et al. (2021) and all its members have hairy nutlets/ovaries. The densely hispid and glandular nutlets of P. hsiwenii and its recovery within Clade III further support that nutlet morphology might be of phylogenetic significance for the infrageneric classification of Paraphlomis (Chen et al. 2021).

Morphologically, P. hsiwenii is most similar to P. pagantha, when comparing it with other species with hairy nutlets. For example, most species of Clade III are characterized by densely hispid or strigose stems and laminas, whereas both P. hsiwenii and P. pagantha have densely hispidulous stems and subglabrous to glabrous laminas (Fig. 3). They also share ovate laminas with serrate margins and triangular calyx teeth (Figs 3, 4). The two species differ mainly in the morphology of lamina bases, which are not decurrent in P. hsiwenii (Fig. 3) but obviously decurrent in P. pagantha. Another difference is that the length of pedicels and calyces is much longer in the new species (Fig. 4). Moreover, the upper corolla lips are ca. 6 mm wide with emarginate apices in P. hsiwenii (Fig. 4), but much narrower (ca. 3 mm wide) with entire apices in P. pagantha. Other morphological differences between the two species can be found in Table 1. Geographically, the new species is now only discovered from the limestone area in Diding Natural Reserve at the Sino-Vietnamese border, whereas P. pagantha usually grows in the evergreen forests in northern Vietnam and Hainan Province, China (Fig. 5). Notably, P. pagantha was treated as a synonym of P. lancidentata Y.Z. Sun by Suddee and Paton (2006). However, the nutlets of P. lancidentata are glabrous and the two species are recovered within different clades in the phylogenetic trees (Figs 1, 2).

Figure 3. 

Morphology of Paraphlomis hsiwenii from the type locality A, B habitat C–E habit F leaves G stolons. Scale bar: 5 cm (A, C photographed by Xiao-Lei Ma B, D, E photographed by Xiong Li F photographed by Ya-Ping Chen G photographed by Jin-Fei Xiao).

Figure 4. 

Floral traits of Paraphlomis hsiwenii. A frontal view of flowers B dorsal view of flowers C lateral view of flowers D lateral view of calyces E frontal view of calyces F dissected calyx G dissected corolla and lateral view of corolla H lateral and frontal view of ovary I lateral view of nutlet. Scale bars: 2 mm (F); 4 mm (G); 500 μm (H) (A–C, G, H photographed by Jin-Fei Xiao D–F photographed by Ya-Ping Chen I photographed by Xiong Li).

Taxonomic treatment

 Paraphlomis hsiwenii Y.P.Chen & XiongLi, sp. nov.

urn:lsid:ipni.org:names:77307630-1

Figs 3, 4

Type

China, Guangxi, Jingxi City, Nanpo Town, Longting, Diding Natural Reserve, among shrubs in forests of limestone area, 23°3'29.55"N, 105°57'13.82"E, alt. 1181 m, 25 Jun 2022, J.F. Xiao & X.L. Ma XJF095 (holotype: KUN!; isotypes: K!, KUN!, MO!, PE!).

Diagnosis

Paraphlomis hsiwenii is morphologically most similar to P. pagantha, but differs in having laminas glabrous above (vs. sparsely strigose above), bases of laminas not decurrent (vs. decurrent), calyces ca. 6 mm long (vs. ca. 4 mm long) with teeth ca. 2 mm long (vs. ca. 1 mm long), and upper corolla lips emarginate at apex (vs. entire at apex).

Perennial herbs 50–120 cm tall, stoloniferous. Stems erect, simple or branched, obtusely 4-angled, densely retrorse hispidulous and glandular. Leaves opposite; lamina ovate, papery, 3–11 × 2.5–5 cm, apex acute to acuminate, margin serrate, base cuneate to broadly cuneate, adaxially green, glabrous, abaxially light green, purplish-green, or purple, densely glandular, lateral veins 3–5-paired; petioles 0.5–2 cm long, densely retrorse hispidulous and glandular. Verticillasters 2–14-flowered; bracteoles subulate, ca. 0.5 mm long, early deciduous; pedicels 2–3 mm long, densely retrorse hispidulous and glandular. Calyx green to yellowish-green, campanulate, ca. 6 mm long, densely hispidulous and glandular outside; teeth 5, subequal, triangular, reflexed, ca. 2 mm long, sparsely hispidulous inside, apex acute. Corolla ca. 1.4 cm long; tube ca. 6 mm long, ca. 1.5 mm wide, purplish-red at upper part; 2-lipped, upper lip oblong, yellowish-green, erect, concave, ca. 8 mm long, ca. 6 mm wide, sparsely pubescent outside, apex emarginate, lower lip ca. 8 mm long, ca. 1 cm wide, sparsely pubescent outside, 3-lobed, medium lob largest, white, dotted with purplish-red spots, subcircular, concave, apex emarginate, ca. 6 mm long, ca. 6 mm wide, lateral lobes ovate, yellowish-green, dotted with purplish-red spots, reflexed, ca. 4 mm long, ca. 2 mm wide. Stamens 4, straight, included, filaments hispid at base, anther cells 2, divergent. Style included, glabrous, apex subequally 2-lobed, lobes subulate. Ovary truncate at apex, densely hispid and glandular. Nutlets yellowish-brown, triquetrous-oblong, ca. 3.5 mm long, apex hispid and glandular.

Phenology

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

Distribution and habitat

Paraphlomis hsiwenii is currently only known from Diding Natural Reserve in Guangxi, China (Fig. 5). It occurs in shady places in evergreen broad-leaved forests or among shrubs in limestone mountains at an altitude of ca. 1200 m.

Figure 5. 

Distribution of Paraphlomis hsiwenii (star) and P. pagantha (circle).

Etymology

The new species is named after the Chinese taxonomist Hsi-Wen Li, who passed away in 2021 and had contributed tremendously to the taxonomy of Lamiaceae from China.

Chinese name

(assigned here). xī wén jiǎ cāo sū (锡文假糙苏).

Additional specimens examined

China. Guangxi: Jingxi City, Nanpo Town, Longdingtun, Diding Natural Reserve, alt. 1231 m, 19 Aug 2020, W.H. Wu et al. DD426 (KUN).

Specimens of P. pagantha examined

China. Hainan: Danzhou City, Shaposhan (Mt. Shamaoling), 29 Aug 1927, W.T. Tsang 672-16171 (IBSC0718446, IBSC0585106, PE00834801); Ledong County, Chang’e Village, Mt. Chang’eling, 16 Jun 1936, S.K. Lau 27154 (IBK00059945, IBSC0585103, KUN0274797, NAS00224460, PE00834800); Ledong County, Mt. Jianfengling, alt. 750 m, 16 Jun 1959, Z.F. Wei 122572 (IBSC0585104); Qionghai City, Huishan Natural Reserve, 21 Apr 2021, L.X. Yuan et al. s.n. (KUN); Wanning City, Xinglong Town, Langmingtian Village, Wutiaosang, 17 Jul 1935, F.C. How 73217 (IBK00059942, IBSC0585105, PE00834802); Wanning City, Xinglong Town, Mt. Niuguling, 16 Apr 1935, F.C. How 71953 (BM, IBK00059943, IBSC0585102); Wanning City, mountain behind Nanlin Nongchang, 5 May 1984, Z.X. Li et al. 1661 (IBSC0585107); Wenchang City, Tongguling Natural Reserve, 4 Aug 2021, L.X. Yuan et al. s.n. (KUN). VIETNAM. Tonkin (Hanoi): Mont. Bavi, Aug 1887, B. Balansa 2914 (Type: K000928198); Ba Vi, Son Tay, alt. 800 m, 14 Jun 1962, Ban 6893 (IBSC0616357).

We would like to thank the staff of the following herbaria for their kind help in research facilities: BM, CDBI, E, GXMI, HIB, IBK, IBSC, K, KUN, KYO, MW, NAS, PE, SZ, TI. Thanks are also given to Mr. Xiao-Lei Ma for his help in field collection, and to the reviewers for their valuable suggestions that improved our manuscript. This work was supported by the National Natural Science Foundation of China (Grant No. 31800168) and the Yunnan Fundamental Research Projects (Grant Nos. 202101AU070067 & 202101AT070159) to YPC. Thanks are also given to Mr. Xiao-Lei Ma for his help in field collection, and to the reviewers for their valuable suggestions that improved our manuscript.