Research Article |
Corresponding author: Guo-Xiong Hu ( gxhu@gzu.edu.cn ) Corresponding author: Xiao-Yu Wang ( xywang2@gzu.edu.cn ) Academic editor: Alan Paton
© 2021 Guo-Xiong Hu, Ting Su, Ming-Tai An, Xiao-Yu Wang.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Hu G-X, Su T, An M-T, Wang X-Y (2021) Rediscovery of Pogostemon dielsianus (Lamiaceae, Lamioideae), a rare endemic species from southwestern China, after one century. PhytoKeys 171: 61-73. https://doi.org/10.3897/phytokeys.171.60389
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Pogostemon dielsianus (Lamiaceae) was described in 1913 based on a single gathering from northwestern Yunnan of China collected in 1905, and thereafter no further collections were observed until 2019. We rediscovered the rare endemic species in Lushui County, Yunnan. Molecular phylogenetic analyses based on four cpDNA markers (rbcL, rps16, psbA-trnH, and trnL-trnF) and the nuclear ribosomal internal transcribed spacer (ITS) region confirmed its infrageneric placement within subg. Pogostemon. Based on observations of the rediscovered population of P. dielsianus, we updated its morphological description, provided an illustration, and discussed its distribution. Under IUCN criteria, the species was categorized as “Critically Endangered (CR)”.
Critically endangered, Nujiang Canyon, Pogostemon elsholtzioides, Pogostemon griffithii, subg. Pogostemon, Yunnan
Pogostemon Desf. is the largest genus of tribe Pogostemoneae of subfamily Lamioideae in Lamiaceae (
In China, 27 species and two varieties were recorded, of which 10 species and one variety are endemic (
During a scientific field trip in Nujiang Canyon, northwestern Yunnan of China in November 2019, a population of Pogostemon was discovered in thickets near a tributary of Nujiang River (also known as Salween River). After scrutiny of the data available (
Following the latest phylogenetic study (
Voucher information and GenBank accession numbers for taxa used in this study. *indicates the new sequences, and “–” indicates missing data.
Taxa | Voucher | GenBank accession numbers | ||||
---|---|---|---|---|---|---|
nrITS | rbcL | rps16 | trnH-psbA | trnL-F | ||
Anisomeles heyneana Benth. | – | – | HQ911589 | – | HQ911659 | |
A. indica (L.) Kuntze | G. Yao 369 (IBSC) | KR608726 | KR608471 | KR608595 | KR608530 | KR608658 |
A. malabarica (L.) R. Br. ex Sims | Fagerlind & Klackenberg 343 (S) | MH456886 | – | FJ854013 | – | FJ854260 |
Pogostemon benghalensis (Burm. f.) Kuntze | R. G. Troth 677 (US) | – | – | HQ911592 | KR608568 | HQ911663 |
P. amaranthoides Benth. | J. Chen 668 (KUN) | KR608745 | KR608490 | KR608614 | KR608549 | KR608677 |
P. aquaticus (C.H. Wright) Press | Bidgood et al. 3387 (K) | KR608767 | KR608527 | KR608655 | KR608592 | KR608717 |
P. auricularius (L.) Hassk. | G. Yao 362 (IBSC) | KR608761 | KR608513 | KR608638 | KR608575 | KR608700 |
P. barbatus Bhatti & Ingr. | G. Yao 274 (IBSC) | KR608762 | KR608514 | KR608639 | KR608576 | KR608701 |
P. brachystachyus Benth. | G. Yao 358 (IBSC) | KR608775 | KR608517 | KR608642 | KR608579 | KR608704 |
P. cablin (Blanco) Benth. | G. Yao 291 (IBSC) | KR608757 | KR608503 | KR608627 | KR608562 | KR608690 |
P. chinensis C.Y. Wu & Y.C. Huang | G. Yao 445 (IBSC) | KR608742 | KR608512 | KR608637 | KR608573 | KR608699 |
P. dielsianus Dunn | Hu et al 636 (GACP) | MW194872* | MW194874* | MW194875* | MW194873* | MW194876* |
P. elsholtzioides Benth. | Syn. s.n. (US sheet no. 262106) | – | – | KR608633 | KR608569 | KR608720 |
P. formosanus Oliver | R. Q. Gao & S. H. Lai 710 (PE) | KR608779 | KR608500 | KR608624 | KR608559 | KR608687 |
P. fraternus Miq. | Syn. 7655 (KUN) | KR608781 | – | KR608648 | KR608585 | KR608710 |
P. glaber Benth. | G. Yao 364 (IBSC) | KR608740 | KR608496 | KR608620 | KR608555 | KR608683 |
P. heyneanus Benth. | G. Yao 297 (IBSC) | KR608751 | KR608492 | KR608616 | KR608551 | KR608679 |
P. hispidocalyx C.Y. Wu & Y.C. Huang | Expedition to QTP 9446 (KUN) | KR608780 | – | KR608644 | KR608581 | KR608706 |
P. linearis (Benth.) Kuntze | G. Yao 348 (IBSC) | KR608764 | KR608521 | KR608649 | KR608586 | KR608711 |
P. litigiosus Doan ex Suddee & A. J. Paton | V. D. Nong 31712077 (IBSC) | KR608776 | KR608519 | KR608645 | KR608582 | KR608707 |
P. macgregorii W. W. Sm. | K.Iwatsuki et al. 9659 (A) | KR608778 | – | – | – | – |
P. paniculatus (Willd.) Benth. | Middleton et al. 1532 (K) | – | – | – | KR608574 | KR608721 |
P. paniculatus (Willd.) Benth. | J. Klackenberg & R. Lundin 565 (S) | – | – | FJ854071 | – | |
P. parviflorus Benth. | G. Yao 365 (IBSC) | KR608749 | KR608501 | KR608625 | KR608560 | KR608688 |
P. petelotii Doan ex G. Yao, Y.F. Deng & X.J. Ge | T. Sorensen et al. 6313 (KUN) | KR608772 | KR608529 | KR608657 | KR608594 | KR608719 |
P. plectranthoides Desf. | G. Yao 449 (IBSC) | KR608758 | KR608510 | KR608635 | KR608571 | KR608697 |
P. quadrifolius (Benth.) F. Muell. | F. G. Dickason 8194(A) | KR608773 | KR608518 | KR608643 | KR608580 | KR608705 |
P. rogersii N E. Br. | Phillips 3855 (K) | KR608782 | – | KR608647 | KR608584 | KR608709 |
P. sampsonii (Hance) Press | G. Yao 273 (IBSC) | KR608769 | KR608524 | KR608652 | KR608589 | KR608714 |
P. septentrionalis C.Y. Wu & Y.C. Huang | G. Yao 264 (IBSC) | KR608747 | KR608497 | KR608621 | KR608556 | KR608684 |
P. stellatus (Lour.) Kuntze | B. Z. Xiao 4826 (K) | KR608768 | KR608523 | KR608651 | KR608588 | KR608713 |
P. xanthiifolius C.Y. Wu & Y.C. Huang | H. T. Tsai 59-10586 (KUN) | KR608746 | KR608493 | KR608617 | KR608552 | KR608680 |
P. yatabeanus (Makino) Press | G. Yao 285 (IBSC) | KR608766 | KR608526 | KR608654 | KR608591 | KR608716 |
Total genomic DNA of Pogostemon dielsianus was extracted from silica gel-dried leaf material following the modified CTAB method of
Sequences were checked and assembled employing Sequencher v.4.1.4 (Gene Codes, Ann Arbor, Michigan, USA) and then aligned Mafft-win v7.221 (
Both nrDNA and cpDNA analyses supported the monophylies of Pogostemon and its two subgenera (subg. Pogostemon and subg. Dysophyllus). Although Pogostemon dielsianus fell into the subg. Pogostemon in both trees, its phylogenetic position was not entirely consistent (Figs
Cladogram of Pogostemon based on ML analysis of internal transcribed spacers (ITS) matrix. Pogostemon dielsianus is highlighted in red. Bootstrap values of ML are given above the branches with posterior probabilities (PP) of BI below. Bootstrap values <40% and PP< 0.6 are indicated by a dash.
Cladogram of Pogostemon based on ML analysis of the combined cpDNA (rbcL, rps16, psbA-trnH, and trnL-trnF) dataset. Pogostemon dielsianus is highlighted in red. Bootstrap values of ML are given above the branches with posterior probabilities (PP) of BI below. Bootstrap values <40% and PP< 0.6 are indicated by a dash.
Morphologically, Pogostemon dielsianus is similar to P. elsholtzioides Benth. and P. griffithii Prain in having lanceolate leaves (
(designated by Bhatti and Ingrouille in Bull. Nat. Hist. Mus. Lond. (Bot.) 27: 99. 1997). China. Yunnan: Fugong, Valley of the Salween, between Shih-chi-ti and Shia-ku-ti, Salween-Irrawaddy Divide, 26°20'N, 1524–1829 m, November 1905, G. Forrest 875 (E [barcode E00087126, image!]; isolectotype: K [barcode K000249619, image!]).
Perennial shrubs, up to 3 m tall. Stems solid, gray, ground diameter to 3.5 cm, branches terete or angular, slightly dilated at nodes, the initial branches green, densely strigose-pubescent, 2–3-year-old branches yellow-brown, subglabrous. Leaves opposite; petiole 0.5–2.5 cm long; blade linear-lanceolate to lanceolate, 8–14 × 2–4 cm, papery, both sides densely strigose-puberulent when young, the mature gradually subglabrous, base cuneate, margin serrate, apex acuminate, lateral veins 3–6 pairs. Spikes 3.5–7 cm long, 8–12 mm wide, terminal and axillary, subcontinuous, basally somewhat lax, with more than two lateral branches, densely appressed pubescent except for corolla, pedunculate, 0.5–2 cm long; cymes sessile, 8–14-flowered, flowers sessile. Bracts 4–6.5 mm, bracteoles 1.8–2.3 mm. Calyx tubular, 3.5–4.5 mm long, 5-veined; teeth 5, triangular, 1/5–1/4 as long as the calyx tube. Corolla rose, 2-liped, 7–9 mm long, glabrous outside; tube cylindric, dilated at throat, ca. 2× as long as calyx; upper lip 3-lobed, lobes triangular, subequal, 1.1–1.3 × 0.9–1.1 mm; lower lip entire, ca. 0.9 × 0.7 mm. Stamens 4, exserted from corolla; filaments 5.5–7 mm long, exserted portion ca. 3.5 mm. Style 6.3–8.5 mm long; stigma bifid, lobes subequal, 1.1–1.3 mm. Disc ca. 0.7 mm long. Nutlets 4, ca. 1.5 × 0.8 mm, lanceolate.
The type locality of Pogostemon dielsianus was recorded in Fugong County, northwestern Yunnan of China, which is the only historical known site until our new discovery. As coordinate information of the collection is incomplete due to the lack of longitude data, the precise situation of type specimen is unclear. Based on the latitude provided in the original record, the type specimen is more likely to be collected in the north of Lushui County, a neighboring county of Fugong (Fig.
Flowering and fruiting from November to December.
Pogostemon dielsianus is historically known from only two specimens collected from the type locality (Fugong, Yunnan, China) in 1905, and it has not been recollected for the past 114 years until our expedition to Nujiang Canyon in 2019. In the newly recorded locality (Lushui, Yunnan, China), only about 10 mature individuals have been discovered. Due to the lack of exact geographical information of the type locality, it is difficult to confirm the number of individuals there. Based on current investigations and historical records, we inferred that mature individuals of this species may be fewer than 250, and no subpopulation contains more than 50 mature individuals. Therefore, under the IUCN criteria C2a(i) (
China. Yunnan: Lushui County, Daxingdi Town, Tuanjie Village, Luchuluo, amongst a thicket near the Luchuluo River, elevation 1786 m, 26°7.14'N, 98°53.78'E, 24 November 2019, Hu et al. 636 (GACP!, IBSC!, KUN!).
Pogostemon dielsianus is morphologically similar to P. elsholtzioides and P. griffithii in having lanceolate leaves. However, P. dielsianus can be easily distinguished from P. elsholtzioides and P. griffithii by its longer and tubular calyx, smaller ratio of the length of calyx teeth and calyx tube and longer corolla, filament and style (Table
Morphological comparison between Pogostemon dielsianus and its morphologically similar species.
Character | Pogostemon dielsianus | Pogostemon elsholtzioides | Pogostemon griffithii |
---|---|---|---|
Calyx | tubular, 3.5–4.5 mm long | campanulate, 3–3.5 mm long | campanulate, ca. 3.5 mm long |
Ratio of the length of calyx teeth and calyx tube | 1/5–1/4 | 1/3–1/2 | 1/2–1 |
Corolla length | 7–9 mm | ca. 4.5 mm | ca. 5 mm |
Filament length | 6.2–7 mm | 4.5–5 mm | 4.7–5.2 mm |
Style length | 6.3–8.8 mm | ca. 5.5 mm | ca. 5.5 mm |
Nutlet | lanceolate | lanceolate | oblong |
Distribution | China (NW Yunnan) | Bhutan, India, China (SE Xizang) | Myanmar |
In the protologue,
We thank Wei Zhang, Yan-Bing Yang and Jin-Zhu Shi for help with field work, Ling-Bin Yan for drawing the geographic distribution map, and two reviewers and the academic editor for their helpful suggestions and comments on how to improve the manuscript. This work was supported by the National Natural Science Foundation of China (32060048 and 31600164).