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. 2026 Jul 25;15(15):2274. doi: 10.3390/plants15152274

Cathetus yuanjiangensis (Phyllanthaceae, Phyllantheae), a New Species from Southwest China, with a New Combination and an Updated Key to C. Subgen. Cathetus

Feng Yang 1, Chao Chen 2,3,4, Zhuo Li 1, Jian-Yong Wu 5, Hui Fan 6, Huan-Chong Wang 1,7,*
Editors: Nikos Krigas, Pepy Bareka
PMCID: PMC13468525  PMID: 42588778

Abstract

Cathetus yuanjiangensis Huan C. Wang, Feng Yang et Chao Chen (Phyllantheae, Phyllanthaceae), a new species from the dry-hot valleys of Southwest China, is described and illustrated herein. Morphologically, the new species can be easily distinguished from its congeners by the following combination of characters: leaves 1.5–4.5 cm long, 1–2 cm wide; staminate flowers sepals spreading 1.5–2.0 mm long; filaments connate into a 2–3 mm long column; styles 3, ca. 1.6 mm long, connate into a ca. 0.5 mm long column at base; stigmas spreading, slender, oblong, each bifid to 1/2, the lobes linear. Phylogenetic analyses based on two nuclear (ITS and PHYC) and three chloroplast (matK, accD-psaI and trnS-trnG) DNA makers recover C. yuanjiangensis as the sister clade to C. fasciculate among the sampled taxa. Detailed morphological descriptions, photographs, pollen morphology, and complete plastid genome characteristics of the new species are provided, along with a distribution map and a preliminary conservation assessment. Additionally, we propose a new combination, Cathetus beillei (Hutch.) Huan C. Wang et Feng Yang, based on the basionym Phyllanthus beillei Hutch., which was originally published in Flora of Tropical Africa. An updated identification key for all recognized species of C. subgen. Cathetus is provided.

Keywords: Phyllantheae, Phyllanthus, Yuanjiang dry-hot valley, plastid genome, phylogeny

1. Introduction

The tribe Phyllantheae is the largest tribe in the family Phyllanthaceae, comprising more than 1200 species [1]. The systematic classification of this tribe has long been plagued by the paraphyly of Phyllanthus s.l. [1]. Since the genus Phyllanthus L. was established by Linnaeus in 1753, Phyllanthus has been treated as a broad group containing nearly 900 species due to convergent morphological characteristics and extremely high morphological diversity [2]. However, recent molecular studies clearly demonstrated that Phyllanthus (in the traditional sense) is paraphyletic since Glochidion J.R. Forst. et G. Forst., Breynia J.R. Forst. et G. Forst. and Synostemon F. Muell. are nested within this clade [3,4,5]. To resolve the paraphyly of Phyllanthus s.l., Bouman et al. [5] proposed a phylogenetic classification that divides Phyllanthus s.l. into several smaller, monophyletic genera that can be characterized morphologically, based on phylogenetic analyses of nuclear genes and plastid genes, altogether with morphological and palynological evidence, particularly pollen morphological characteristics. The classification system of Bouman et al. [5] has been accepted by many studies [6,7,8,9,10], while others still accept and use paraphyletic Phyllanthus s.l. [11].

Cathetus Lour. was first formally described by Loureiro in 1790 based on the type species Cathetus fasciculata Lour. (later synonymized with the formerly recognized Phyllanthus cochinchinensis Spreng.) [12]. For over a century thereafter, Cathetus was subsumed in the genus Phyllanthus s.l. [5]. Subsequent classifications [13,14,15] retained this broad circumscription, treating Cathetus allied taxa as subgenera or sections of Phyllanthus s.l. It was not until 2022 that Bouman et al. reinstated and redefined Cathetus as an independent genus [5]. The reinstated and redefined genus Cathetus includes two phylogenetically supported subgenera, namely subgen. Cathetus and subgen. Macraea (Wight) R.W. Bouman. Among them, subgen. Cathetus (formerly P. subgen. Ceramanthus (Hassk.) Brunel) consists of six species, characterized by the complete fusion of stamen filaments and connectives forming a staminal column, pantoporate or brevicolporate pollen grains, and a coarsely reticulate exine. Subgen. Macraea (formerly P. subgen. Macraea (Wight) Baillon) includes 34 species, distinguished by free or basally connate stamen filaments, poriform (peltate) pollen apertures, typically distichous leaves, and a growth habit ranging from herbs and subshrubs to trees. The newly delimited Cathetus has an Old World tropical and subtropical distribution, occurring in Africa, mainland Asia, the Malay Archipelago, Australia and the Pacific region.

There are five species native to China, namely Cathetus filipes D. X. Nong, B.Y. Huang &et Z. Xiong, C. clarkei (Hook.f.) R.W. Bouman, C. fasciculata, C. ussuriensis (Rupr. et Maxim.) R.W. Bouman, and C. virgatus (Forster) R.W. Bouman. In addition, C. myrtifolius (Wight) R.W. Bouman, native to Sri Lanka, has been introduced for ornamental cultivation [10,16]. Cathetus is also widely distributed in China, and is found in all provinces and regions except the northwest region. Nevertheless, the diversity and taxonomy of this genus in China remain poorly understood. During our recent fieldwork in China, an unknown species of Cathetus with large leaves was encountered in Yuanjiang Valley, Yunnan Province. After a detailed study of its morphology and analysis of relevant literature [5,16,17,18,19,20,21,22,23], we hypothesized that this plant represents a new species of Cathetus.

In the present study, we formally describe this plant as a new species, namely Cathetus yuanjiangensis Huan C. Wang, Feng Yang et Chao Chen sp. nov., providing photographs, pollen morphology, a plastid genome, a distribution map, a preliminary conservation assessment, and taxonomic notes. Phylogenetic analysis based on nuclear (ITS and PHYC) and chloroplast (matK, accD-psaI and trnS-trnG) sequence data was conducted to test the phylogenetic placement of C. yuanjiangensis within Cathetus. Additionally, we herein propose a new combination, C. beillei (Hutch.) Huan C. Wang et Feng Yang comb. nov., based on the basionym Phyllanthus beillei Hutch., which was originally published in Flora of Tropical Africa by Hutchinson in 1912. An updated identification key for all currently recognized species of the subgen. Cathetus is presented.

2. Results

2.1. Characteristics of the Plastid Genome, nrDNA and PHYC

The complete plastid genome sequences of Cathetus yuanjiangensis comprised 152,879–153,997 bp. Each genome had the circular and typical quadripartite structure and contained a large single-copy region (LSC, 83,243–83,353 bp), a small single-copy region (SSC, 17,996–18,004 bp), and two inverted sequence repeat regions (IRs, 25,761–26,379 bp each) (Figure A1). The percentage of GC in the whole genome was 37.0%. We annotated a total of 128 functional genes, including 85 protein-coding genes, 36 tRNA genes, and 8 rRNA genes (Figure A1, Table A1). These plastid genomes were used as a source of matK, accD-psaI and trnS-trnG in the phylogenetic analyses. The assembled nrDNA repeats, including the ETS, 18S, ITS1, 5.8S, ITS2, and 26S regions, were 8884–8903 bp in length, with a GC content of 55.2%. All PHYC genes were 718–805 bp in length, with a GC content of 41.6–42.1%. The newly generated plastid genome, nrDNA and PHYC sequences have been deposited in GenBank (Table A2).

2.2. Molecular Phylogenetic Analysis

The alignment length of the concatenated nuclear set was 1486 bp, and the percentage of parsimony informative sites was 22.01%. The concatenated three plastid regions had a length of 2457 bp for phylogenetic analysis, with 11.19% parsimony informative sites. Similar topologies were obtained in the Maximum Likelihood (ML) and Bayesian Inference (BI) analyses using two different matrix sequences of concatenated molecular markers (Figure 1 and Figure 2).

Figure 1.

Figure 1

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The phylogenetic position of Cathetus yuanjiangensis in the genus Cathetus based on ML and BI methods using concatenated matrix sequences from two nuclear markers, ITS and PHYC. The positions of C. yuanjiangensis are marked by red text. The asterisk (*) indicates nodes not supported in ML phylogenetic tree.

Figure 2.

Figure 2

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The phylogenetic position of Cathetus yuanjiangensis in the genus Cathetus based on ML and BI methods using concatenated matrix sequences from three plastid markers: matK, accD-psaI and trnS-trnG. The positions of C. yuanjiangensis are marked by red text. The asterisk (*) indicates nodes not supported in ML phylogenetic tree.

The phylogenetic trees recovered Cathetus as two major highly supported lineages. Eleven sampled species from subgenus Macraea formed clade I. Clade II lineage could be further divided into two sub-clades. Sub-clade A included C. clarkei and one taxon allied to C. fasciculata, whereas sub-clade B consisted of an Asian clade and an African clade. Within the Asian clade, all accessions of C. yuanjiangensis formed a strongly supported lineage (Figure 1 and Figure 2: 100%/1) and were recovered as sister to C. fasciculata among the sampled taxa (Figure 1: 76%/0.96; Figure 2: 93%/1). Within the African clade, C. beillei was recovered as the likely sister of C. kerstingii, but this relationship had low support and differed between the ML and BI analyses (Figure 1: 57%/*; Figure 2: 71%/0.71). Cathetus petraeus occupied a more basal position as sister to the clade containing C. beillei and C. kerstingii (Figure 1: 79%/0.99; Figure 2: 98%/1).

2.3. Taxonomic Treatment

Cathetus yuanjiangensis Huan C. Wang, Feng Yang et Chao Chen sp. nov. (Figure 3, Figure 4 and Figure 5).

Figure 3.

Figure 3

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Anatomical diagram of Cathetus yuanjiangensis (voucher: Chao Chen YJ31054, YUKU). (A–G) Staminate flowers and related structures; (A) lateral view of staminate flower; (B) top view of staminate flower; (C) staminate flower with stamens removed, showing 6 disc glands, one of which has fallen off; (D) dorsal view of a staminate flower; (E) filaments connate into a column; (F) Dehiscing anthers; (G) a disc gland. (H–O) Pistillate flowers and fruits; (H) lateral view of pistillate flower; (I) top view of pistillate flower; (J) disc, pistil and stigma of a pistillate flower; (K) young fruit; (L) lateral view of mature fruit; (M) mature fruit with fruit removed, showing the persistent disc and calyx; (N) dorsal view of pistillate flower; (O) cross-section of fruit. (P) Seeds, showing lateral, dorsal, and ventral views (from left to right). (Q) Staminate flowers (♂) fasciculata in leaf axils. (R) Pistillate flowers (♀) fasciculata in leaf axils. (S) Branchlet. (T) Stipules. (U) Bracts. (V) Adaxial and abaxial surfaces of leaves.

Figure 4.

Figure 4

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SEM micrograph of stamen and pollen morphology of Cathetus yuanjiangensis sp. nov. (voucher: Huan C. Wang et al. YJ31040, YUKU). (A) General view of the stamen, showing longitudinal dehiscence; (B) a group of scattered pollen grains; (C) close-up view of pollen grain, showing the reticulate exine ornamentation.

Figure 5.

Figure 5

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Distribution and habitat of Cathetus yuanjiangensis. (A) GeoCAT distribution map of Cathetus yuanjiangensis and estimation of extent of occurrence (EOO) and area of occupancy (AOO); (B) plant (voucher: Huan C. Wang YJ32404, YUKU); (C) habitat of the population found in Wadie.

Type: China. Yunnan Province: Yuxi City, near Yuanjiang County, Mount E’ka, 23°39′7.4″ N, 102°0′19.1″ E, 731 m, 6 September 2025, fl. and fr., Huan C. Wang et al. YJ31040 (Holotype: YUKU02074913!; Isotypes: KUN!, PE!, YUKU02074914!, YUKU02074915!).

Diagnosis: Morphologically, Cathetus yuanjiangensis is most similar to C. beillei, but differs clearly from the latter by being a small shrub, up to 50 cm high (vs. shrub, up to 3 m high in C. beillei), branchlets glabrous (vs. sparsely papillose-puberulent), stipules caducous (vs. more or less persistent), styles ca. 1.6 (vs. 0.5–0.8) mm long, connate into a ca. 5 (vs. 0.7) mm long column at base, stigmas spreading, slender, oblong, each bifid to 1/2 (vs. fleshy, triangular in outline, apex shallowly or deeply lobed, ca. 1 mm long).

Description: Evergreen small shrub, up to 50 cm tall, glabrous throughout. Stems several from a woody rhizome, much branched, branching non-phyllanthoid, 10–50 cm long, 1–2 mm in diam., purplish-red, reddish-brown, or grey-green when fresh, grey or greyish brown when old, bark peeling longitudinally into narrow strips. Leaves distichous, alternate, coriaceous, obovate-oblong or spatulate, 1.5–4.5 cm long, 1–2 cm wide, L/W ratio 1.5–2.25, on the lower parts of branchlets smaller, apex round, rarely retuse, base attenuate, cuneate to cordate, margin entire, slightly revolute when dry, adaxially green, abaxially greyish green; venation reticulate, conspicuous on both surfaces, lateral veins 15–20 pairs, midvein conspicuous abaxially; petiole short and stout, 1–2 mm long; stipules reddish-brown, ovate-triangular, membranous, ca. 2 mm long, base enlarged and auriculate, apex subulate to filiform, margin fimbriate or laciniate, caducous. Dioecious; flowers 1–3 per axil, borne on cushion-like swellings, base of swellings with numerous bracts; bracts similar to stipules, membranous, reddish-brown, deeply lacerate-fimbriate at base, persistent. Staminate flowers: 1–2 clustered; pedicel 3–5 mm long; sepals spreading, pale yellow, subhyaline, 6, 2-seriate, unequal, inner slightly longer than outer, outer 3 ovate-rhombic, inner 3 oblong, 1.5–2.0 mm long, 1.0–1.5 mm wide, margin membranous, nearly white, entire or lacerate, base thickened; stamens 3; filaments connate into a column, 2–3 mm long; anthers 3, ca. 0.6 mm long, perpendicular to filament column, longitudinally dehiscent; disc glands 6, on the inner sepals, pale yellow, semi-transparent. Pistillate flowers: 1–3 clustered; pedicel 5–7 mm long; sepals 6, slightly spreading, spaced evenly, 2-seriate, unequal, ovate-rhombic, 1.5–2.0 mm long, 1.0–1.5 mm wide, dark green or yellow-green, margin membranous, white, entire, base thickened, apex obtuse, distinct reticulate veins on sepals; styles 3, ca. 1.6 mm long, connate into a ca. 0.5 mm long column at base, stigmas spreading, slender, oblong, each bifid to 1/2, the lobes linear, recurved, spreading at less than 90°, brown in fruit stage; disc annular, encircling ovary; ovary globose, ca. 1 mm in diam., 3-loculed. Capsule subglobose, trigonous, ca. 6 mm in diam., ca. 4 mm thick, persistent sepals reflexed, apex umbilicate, with remnant black styles; pericarp thin, scabrous, with vermiform raised sculpturing, dark green or olive-green, glossy; surface with 3 ridges, depressed between ridges dividing into 3 carpels, dehiscing at maturity and separating from woody endocarp; each carpel 2-loculed, 1 seed per locule. Seeds light yellowish-brown or dark castaneous, trigonous-compressed globose or triangular-reniform, ca. 3 × 3 × 3 mm; testa thin, cells with prominent dark, domed centers.

Pollen morphology: The pollen grains of Cathetus yuanjiangensis are irregularly spherical, 25.08–28.77 × 21.74–26.90 µm, pantoporate, with a coarsely reticulate pattern on the surface (Figure 4). Ectoapertures usually irregular, slightly elongated pori, in shape resembling the lumina of the reticulum.

Distribution, habitat and conservation assessment: Cathetus yuanjiangensis is a rarely and poorly collected species endemic to the central Yunnan Province in Southwest China. As of now, it has been discovered in five different sites, all situated in the dry and hot valleys of the Yuanjiang River. This species typically inhabits moist streamside habitats, forest understories and margins of seasonal rainforests, at elevations of 500–1000 m (Figure 5). It has a restricted geographic range, with an estimated extent of occurrence (EOO) of 152.64 km2 and an area of occupancy (AOO) of 20 km2 (Figure 5). Based on IUCN Red List Categories and Criteria, we recommend that this species be listed in the Vulnerable (VU) category.

Phenology: The flowering and fruiting period is from July to December.

Etymology: The specific epithet “yuanjiangensis” is derived from the type locality of the new species, i.e., Yuanjiang County, Yunnan Province, China and the Latin suffix ensis, indicating the place of origin or growth.

Chinese name: Yuán Jiāng Shān Gé Mù, ㄩㄢˊ ㄐㄧㄤ ㄕㄢ ㄍㄜˊ ㄇㄨˋ (元江山格木).

Additional specimen examined (paratypes): China. Yunnan Province: Yuxi City, Yuanjiang County, Wadie Township, 23°29′21.39″ N, 102°12′16.73″ E, 897.58 m, 6 September 2025, fl., Chao Chen YJ31054 (YUKU); Yuanjiang County, Xiaoganba, 23°42′14.99″ N, 101°58′34.78″ E, 935.93 m, 21 September 2025, fl., Huan C. Wang YJ32404 (YUKU); Yuanjiang County, Shidie village, 23°33′30″ N, 102°5′4″ E, 977 m, 7 March 2026, nutrition period, Huan C. Wang et al. YJ33172 (YUKU); Yuanjiang County, Mandanqian Mountain, in savanna, under the forest, 23°41′27.62″ N, 101°52′17.15″ E, 740 m, 22 August 2012, fr, Yuanjiang County Census Team 5304281120 (IMDY0007449).

Cathetus beillei (Hutch.) Huan C. Wang et Feng Yang comb. nov.

≡ Phyllanthus beillei Hutch., D. Oliver et auct. suc. (eds.), Fl. Trop. Afr. 6(1): 733, 1912; Phyllanthus welwitschianus var. beillei (Hutch.) Radcl.-Sm., Kew Bull. 35: 775, 1980.

Types: Central African Republic. Source of the Ndelli River, 15–20 December 1902, Chevalier 6846 (lectotype: P, designated by Brunel and Roux [18]; isolectotype: K000406102!). Additional syntype: Central African Republic, Dar Banda, between Kaga Djé and the middle Bamingui, 5 December 1902, Chevalier 6612 (P, BR0000006243210!).

= Phyllanthus stolzianus Pax et Hoffm. ex Pax, Engl. Pflanzenw. Afr. 3(2): 27, 1921.

Types: Tanzanie. environs de Tukuyu (Kyimbila), 900 m, A. Stolz 1404 (Holotype: B, designated by Brunel and Roux [18]; Isotypes: C, HBG515876!, K, LD1403617, M0110580!, WAG0001374!).

= Phyllanthus nyassae Pax et K.Hoffm., Notizbl. Bot. Gart. Berlin-Dahlem 10: 383, 1928.

Types: Tanzanie. Nyassa-Hochland, Station Kyimbila, 900 m, A. Stolz 1891 (HBG515877!, JE00019679!, LD1403677!, M-0110581!).

= Phyllanthus grahamii Hutch. et M.B. Moss, Bull. Misc. Inform. Kew 1937: 413, 1937.

Types: Kenya. Arabuko, in forest undergrowth, 1927, R.M. Graham 1986 (Holotype: K, designated by Brunel and Roux [18]; Isotypes: Br, LISJC, P00539746!, PRE0487071-0!).

2.4. Key to Species of Cathetus Subgenus Cathetus

  • 1a Leaf apex acute......................................................................................................................... 2

  • 1b Leaf apex obtuse or mucronulate......................................................................................... 3

  • 2a Young branches with a broad line of short crisped hairs along each side; staminate flowers with 4 sepals, 2 stamens, and 4 disk-glands............................ Cathetus petraeus

  • 2b Branchlets completely glabrous; staminate flowers with 6 sepals, 3 stamens, and 6 disk-glands................................................................................................... Cathetus gracilis

  • 3a Staminate flowers with 5 sepals and 5 disk-glands..................................... Cathetus binhii

  • 3b Staminate flowers with 6 sepals and 6 disk-glands............................................................ 4

  • 4a Plant a small shrub or more commonly a hemicryptophyte; leaf apex mucronulate................................................................................... Cathetus welwitschianus

  • 4b Plant small shrub or more commonly shrubby; leaf apex rounded................................. 5

  • 5a Leaves smaller, 1–2 cm long, 0.6–1.3 cm wide....................................... Cathetus fasciculata

  • 5b Leaves larger, 1.5–7 cm long, 1–2 cm wide.......................................................................... 6

  • 6a Stigma lobes thick and fleshy.......................................................................... Cathetus beillei

  • 6b Stigma lobes distinctly spreading and slender.................................................................... 7

  • 7a Leaf blade oblong-elliptic or narrowly obovate, 1.5–4 cm long, ca. 1 cm wide, L/W ratio 1.5–4; stigma lobes spreading at 180°, 0.1–0.2 mm long........... Cathetus kerstingii

  • 7b Leaf blade oblong or spathulate, 1.5–4.5 cm long, 1–2 cm wide, L/W ratio 1.5–2.25; stigma lobes spreading at less than 90°, ca. 0.5 mm long......... Cathetus yuanjiangensis

3. Discussion

3.1. Generic Reassignment of Phyllanthus beillei Hutch

Phyllanthus beillei Hutch. was described by Hutchinson in 1912 based on two specimens collected from the Central African Republic [24]. Airy Shaw [25] noted that P. stolzianus Pax et K. Hoffm, P. nyassae Pax et K. Hoffm, and P. grahamii Hutch. et M.B. Moss should all be treated as synonyms of P. beillei. He further suggested that it was conspecific with a large-leaved variety of P. fasciculatus (Lour.) Muell.-Arg. (syn. Cathetus fasciculata) from northern Thailand and Cambodia, as cited by Beille [26] in Flore Générale de l’Indo-chine. Additionally, he observed a close relationship between P. beillei and P. welwitschianus Muell. Arg. Following an extensive examination of specimens from these and related taxa, Airy Shaw [27] formally merged P. beillei and its synonyms into P. welwitschianus. However, this taxonomic revision has not gained broad acceptance. While Radcliffe-Smith [28] proposed downgrading P. beillei to a subspecies of P. welwitschianus, the majority of authors maintain its status as a distinct species [18,20,21,29,30]. Based on specimen examination, morphological observation, palynology, and scanning electron microscopy evidence, Brune and Roux [18] confirmed that P. beillei was clearly different from P. welwitschianus by the habit (hemicryptophyte vs. shrub), plant height (≤0.5 m vs. up to 3 m), leaf base (truncate to subcordate vs. broadly cuneate to rounded), lateral vein (6–14 pairs vs. 12–23 pairs), staminal column length (1.3–1.6 mm vs. 0.5–0.7 mm), stigma lobes (thick and slightly spreading vs. slender and distinctly reflexed), and capsule size (7.5–8.0 mm vs. 6.5–7.0 mm) (Table 1). In this study, relevant specimens and field photographs of P. welwitschianus and P. beillei were examined. The results showed that there are stable and significant diagnostic characters between the two taxa, so we agree with the viewpoint of Brune and Roux [18] and treat them as distinct species. Recently, Bouman et al. [5], dealing with the genus Cathetus, left out and did not transfer P. beillei to Cathetus. Therefore, we propose transferring it to the genus Cathetus via a new taxonomic combination: Cathetus beillei (Hutch.) Huan C. Wang et Feng Yang.

Table 1.

Qualitative character comparison among Cathetus yuanjiangensis, C. fasciculata, C. welwitschianus, C. beillei and C. kerstingii.

Characters Species
C. yuanjiangensis C. fasciculata C. welwitschianus C. beillei C. kerstingii
Habit Evergreen small shrub, up to 50 cm tall Shrub, up to 3 m tall Erect perennial herb or subshrub, up to 90 cm tall Small much-branched shrub, up to 3 m tall Shrubby, up to 1.5 m tall
Indumentum Glabrous throughout Young branchlets yellowish brown pubescent, glabrescent with age; petioles velvety-papillate Glabrous or finely pubescent Branchlets sparsely papillose-puberulent, glabrescent elsewhere; petioles papillose-puberulent Young branchlet apices pubescent, bark peeling longitudinally in narrow strips with age, branchlets glabrous
Leaf Morphology Coriaceous, obovate-oblong to spatulate, 1.5–4.5 cm long, 1–2 cm wide, L/W ratio 1.5–2.25; apex obtuse-rounded, rarely retuse; base attenuate, cuneate to cordate Coriaceous, obovate, oblong-obovate or spathulate, 1–2 cm long, 0.6–1.3 cm wide; apex obtuse-rounded, very rarely retuse; base attenuate Subcoriaceous, suborbicular to elliptic-oblong, 0.5–3.5 cm long, 0.3–2.8 cm wide; apex rounded to retuse, sometimes mucronulate; base rounded, truncate and subcordate Subcoriaceous, oblong-elliptic or narrowly obovate, 2–5 cm long, 1–2 cm wide; apex rounded; base broadly cuneate Membranous, oblong-elliptic to narrowly obovate, 18–25 mm long, 7–15 mm wide; apex rounded; base rounded to broadly cuneate
Venation Reticulate veins distinct on both surfaces, lateral veins 15–20 pairs, midrib more prominent abaxially Midrib slightly prominent on both surfaces, lateral veins obscure Lateral veins 6–18 pairs, nearly obscure or slightly distinct adaxially, more distinct abaxially Lateral veins ca. 11 pairs per side, slightly prominent, spreading, reticulate Lateral veins 12–20 pairs, slightly prominent abaxially, reticulate
Stipule Reddish brown, membranous, ovate-triangular, base enlarged and auriculate, apex subulate to filiform, ca. 2 mm long, margin fimbriate or laciniate, caducous Reddish brown, ovate-triangular, ca. 2 mm long, base cordate, margin ciliate, apex caudate-acuminate, persistent - More or less persistent, subulate-triangular, 4 mm long, 1 mm wide at base, apex filiform, usually brown-ciliate Scarious, narrow-triangular, base auriculate, 1.3–3.7 mm long, 0.9–1.0 mm wide at insertion, persistent
Staminate flower Sepal 6, spreading, 2-seriate and unequal; outer ovate-rhombic, inner oblong, 1.5–2.0 mm long, 1–1.5 mm wide, margin membranous and subwhite, base thickened 6, obovate to spathulate, ca. 1.3 mm long, 1–1.2 mm wide, base thickened, margin membranous 6, white to yellowish green with red 6, 2-seriate, broadly elliptic, ca. 3 mm long, apex rounded to truncate, glabrous 6,2-seriate, dimorphic; outer membranous, 0.8–1.1 mm long; inner fleshy, apex truncate, 0.7–1.1 mm long, all 0.6–1.0 mm wide
Stamen 3, filaments connate into a column 2–3 mm long; anthers 3, ca. 0.6 mm long, perpendicular to filament column, longitudinally dehiscent 3, filaments connate to the middle; thecae parallel, longitudinally dehiscent 3, filaments connate into a column 2 mm long 3, filaments connate into a column 0.4–0.5 mm long; anthers pendulous, 0.4–0.5 mm long, apices connate
Pistillate flower Sepal 6, slightly spreading, 2-seriate, ovate-rhombic, 1.5–2.0 mm long, 1.0–1.5 mm wide, dark green or yellowish green, margin membranous and white, base thickened, with distinct reticulate veins 6, ovate or ovate-rhombic, 1.5–1.8 mm long, ca. 1.5 mm wide, margin membranous, base thickened 6, white to yellowish green with red, size not mentioned 6, spreading, 2-seriate, broadly elliptic or suborbicular, 3 mm long, apex rounded or subtruncate, glabrous, with distinct venation 6, dimorphic; outer 1.6–2.0 mm long, 1.3–1.5 mm wide; inner 1.8–2.0 mm long, 1.7–1.9 mm wide, with branched midrib
Style 3, ca. 1.6 mm long; lower part connate into a column 0.5 mm long, stigmas spreading, slender, oblong, each bifid to 1/2, lobes linear, spreading at less than 90° 3, ca. 1.1 mm long, connate from middle to base, apex bilobed and recurved - 3, connate into a column 0.7 mm long; stigmas 3, spreading and fleshy, triangular in outline, apex lobed, lobes ca. 1 mm long, thick and fleshy 3, basal part connate into a column 0.1–0.3 mm long; lobes spreading at 180°, slender and cylindrical, 0.1–0.2 mm long, brown in fruit stage
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3.2. The Plastid Genome Sequence of Cathetus yuanjiangensis

The plastid genome data were included primarily to facilitate phylogenetic analyses and comparative genomic assessment. The newly assembled plastomes provided the matK, accD-psaI, and trnS-trnG sequences incorporated into the plastid phylogenetic dataset. Furthermore, this study is the first to report the plastid genome for the new species. The genome structure and gene repertoire of the newly assembled plastid genome of Cathetus yuanjiangensis exhibited high consistency with previously published plastid genomes from other representative taxa of Phyllanthaceae, especially the congeneric species C. clarkei [31]. Notably, the intron loss of the atpF gene was also observed in C. yuanjiangensis, which was shared with C. clarkei and most other Phyllanthaceae species. In addition, no major structural rearrangements, gene losses or large-scale inversions were detected in the plastid sequence of C. yuanjiangensis when compared with these reference genomes. These data therefore support phylogenetic marker recovery and provide genomic resources for future comparative work in Cathetus, but they are not treated here as independent diagnostic evidence for species delimitation.

3.3. Phylogeny of Cathetus and Position of C. yuanjiangensis

The sampled species of Cathetus were recovered as a well-supported monophyletic group and were divided into two major highly supported clades in both nuclear and plastid phylogenetic trees, broadly consistent with the results of previous studies [3,30,32]. In the taxonomic treatment by Bouman et al. [5], these two clades were formally named subgen. Cathetus and subgen. Macraea. Our phylogenetic analyses recovered Cathetus to two major clades. One major clade comprised only members of subgen. Macraea, whereas the other included all sampled species of subgen. Cathetus, which were recovered as a sister group to a lineage containing C. clarkei (currently placed in subgen. Macraea) and a species allied to C. fasciculata. The placement of C. clarkei outside the main Macraea lineage renders subgen. Macraea, as currently circumscribed, polyphyletic. Accordingly, the circumscription of subgen. Macraea requires further re-evaluation.

Cathetus yuanjiangensis was placed within the clades corresponding to subgen. Cathetus, a placement further supported by both morphological and palynological evidence. Within this subgenus, C. yuanjiangensis was recovered as sister to the Asian species C. fasciculata. It shows a more distant relationship with African species such as C. beillei and C. kerstingii. These results provide clear support for assigning C. yuanjiangensis to subgen. Cathetus. However, because molecular data are currently available for only a limited proportion of the species attributed to this subgenus, the inferred sister relationship between C. yuanjiangensis and C. fasciculata should be regarded as provisional rather than as evidence that C. fasciculata is necessarily its closest extant relative. Subgen. Cathetus is distributed throughout the Old World tropics [5], but the relationships and divergence history of its Asian and African lineages remain poorly resolved. Denser taxon sampling across the geographic range of the subgenus, particularly from the Malay Archipelago and Australia, together with explicit biogeographic analyses, will be needed to clarify the origin and dispersal history of these lineages.

3.4. Morphological Distinctiveness of Cathetus yuanjiangensis

According to Bouman et al. [5], Cathetus yuanjiangensis should be assigned to C. subgen. Cathetus due to its stamen filaments completely connate into a column. Prior to the present study, only one species of the subgenus Cathetus was recorded in China, namely C. fasciculata. Indeed, C. yuanjiangensis forms a strongly supported sister clade with C. fasciculata in both the phylogenetic tree constructed based on the chloroplast data matrix and the nuclear gene data matrix. Despite their close phylogenetic placement, C. yuanjiangensis is morphologically distinct from C. fasciculata and all of its synonyms, including P. serissifolius Wall. ex Müll.Arg., P. cinerascens Hook. et Arn. and P. roeperianus Wall. ex Müll.Arg. Cathetus yuanjiangensis has relatively larger leaves, 1.5–4.5 cm long, 1–2 cm wide, staminate flowers with spreading sepals, 1.5–2.0 mm long, filaments connate into a column, ca. 2–3 mm long, longer than the sepals, styles 3, ca. 1.6 mm long, connate into a ca. 5 mm long column at base, stigmas spreading, slender, oblong, each bifid to 1/2, the lobes linear. In contrast, C. fasciculata has smaller leaves, 1–2 cm long, 0.6–1.3 cm wide, staminate flowers sepals arranged in a campanulate form, ca. 1.3 mm long, filaments connate into a column, shorter than the sepals, styles ca. 1.1 mm long, connate at middle to base, bifid at apex, lobes oblong.

Practically, Cathetus yuanjiangensis is most similar to C. beillei in terms of morphology, which is widely distributed in Tropical Africa and Indo-China (Cambodia and Thailand) [18]. However, it differs clearly from C. beillei by being a small shrub, up to 50 cm high (vs. shrub, up to 3 m high in C. beillei), branchlets glabrous (vs. sparsely papillose-puberulent), stipules caducous (vs. more or less persistent), styles ca. 1.6 (vs. 0.5–0.8) mm long, connate into a ca. 5 (vs. 0.7) mm long column at base, stigmas spreading, slender, oblong, each bifid to 1/2 (vs. fleshy, triangular in outline, apex shallowly or deeply lobed, ca. 1 mm long). Cathetus yuanjiangensis is also morphologically similar to C. kerstingii (Brunel) R. W. Bouman from West Tropical Africa. Cathetus yuanjiangensis differs from C. kerstingii in having obovate-oblong to spatulate leaves (vs. oblong-elliptic or narrowly obovate-membranous), L/W ratio 1.5–2.25 (vs. 1.5–4.0), styles ca. 1.6 (vs. 0.2–0.5) mm long, stigma lobes ca. 0.5 (vs. 0.1–0.2) mm long, spreading at less than 90° (vs. at 180°). A qualitative characters comparison between C. yuanjiangensis, C. fasciculata, C. beillei and C. kerstingii is listed in Table 1.

Notably, the comparison also reveals a morphological-molecular incongruence. Cathetus beillei is the most similar species morphologically with C. yuanjiangensis, whereas C. fasciculata is the closest sampled relative in both nuclear and plastid trees. The similarity between C. yuanjiangensis and C. beillei is concentrated mainly in the shape and size of the leaf blade, which should probably be the result of convergent evolution, as they are harbored in the understory of forests in arid zones.

Pollen grains of Cathetus yuanjiangensis are irregularly spherical, measuring 25.08–28.77 × 21.74–26.90 µm. They are periporate with a coarse reticulate exine ornamentation, conforming to the “Phyllanthus cochinchinensis type” as defined by Punt [30]. This pollen morphology supports the placement of C. yuanjiangensis within C. subgen. Cathetus and is consistent with the pollen types of closely related taxa [18,26,33,34,35]. This congruence in pollen morphology demonstrates evolutionary stasis (or conservatism) of palynological traits within this lineage.

3.5. Conservation Assessment of Cathetus yuanjiangensis

Based on the assessment using the GeoCAT tool [36], the extent of occurrence (EOO) of Cathetus yuanjiangensis is 152.164 km2, and its area of occupancy (AOO) is only 20 km2. Fortunately, five known distribution sites are situated within the Yunnan Yuanjiang National Nature Reserve, ensuring that the wild population receives effective in situ protection. Based on the IUCN Red List criteria [37], it should be classified as a Vulnerable (VU) species. Furthermore, ex situ conservation efforts are underway; the Xishuangbanna Tropical Botanical Garden (XTBG) has successfully introduced and cultivated this species under introduction number 0020091695, and the Yuanjiang Savanna Ecosystem Research Station has also achieved successful introduction and cultivation. Leveraging a mature ex situ conservation system, XTBG provides a stable cultivation environment, effectively safeguarding the species against catastrophic extinction of wild populations due to stochastic events or human destruction. The Yuanjiang Savanna Ecosystem Research Station is located within the Yuanjiang River basin. Its climate and soil types are highly congruent with the native habitats of C. yuanjiangensis, facilitating better post-introduction adaptation and maximizing the preservation of the species’ innate adaptive traits. This establishes a solid foundation for future reintroduction. This dual-site introduction model has successfully established a double guarantee for the ex situ conservation of C. yuanjiangensis.

4. Materials and Methods

4.1. Morphological and Taxonomic Analyses

The morphological studies of the new species were conducted on living plants and specimens coming from the five localities corresponding to the type and paratypes. Digital images of this genus are available at online databases, including the iNaturalist (https://www.inaturalist.org), the Tropicos (www.tropicos.org), the JSTOR Global Plants (http://plants.jstor.org/), the Global Biodiversity Information Facility (GBIF, https://www.gbif.org/, accessed on 20 July 2026), and the Chinese Virtual Herbarium (CVH, https://www.cvh.ac.cn/), as well as collections housed at CDBI, IBSC, KUN, PE and YUKU; these were extensively examined and compared with the new species. Pertinent taxonomic literature was consulted [5,16,17,18,19,20,21,22,23].

Morphological data for Cathetus kerstingii (J.F.Brunel) R.W.Bouman [18], C. binhii (Thin) R.W.Bouman [19], and C. petraeus (A.Chev. et Beille) R.W.Bouman [38] were extracted from their respective protologues. Morphological characters for C. gracilis (Hassk.) R.W.Bouman were extracted from the descriptive treatment of Phyllanthus albidiscus (Ridl.) Airy Shaw provided by van Welzen and Chayamarit [22]. Descriptions of C. welwitschianus (Müll.Arg.) R.W.Bouman and C. beillei follow Brune and Roux’s revision [18]. We adopt the species circumscription of C. fasciculata proposed in the taxonomic revision by Chakrabarty and Balakrishnan [39,40], which excludes Phyllanthus roeperianus Wall. ex Müll.Arg. Morphological data for this taxon are retrieved from Flora Reipublicae Popularis Sinicae [17].

4.2. Palynological Studies

For palynological comparison with morphologically similar species, the pollen grains of Cathetus yuanjiangensis were observed under a scanning electron microscope. Mature pollen grains of the new species were sampled from the type materials and attached directly to carbon adhesive tape. They were coated with gold-palladium using a BAL-TEC SCD 005 cool sputter coater (BAL-TEC AG, Balzers, Liechtenstein) at Yunnan University, Kunming, China. Observations were conducted using a Regulus 8100 scanning electron microscope (SEM) (Hitachi, Tokyo, Japan) at 3.0 KV at a magnification of 3.00 K×. Descriptive terminology for the pollen grains follows Punt et al. [30].

4.3. Conservation Assessment

Conservation status was assessed using GeoCAT (online tool available at https://geocat.iucnredlist.org/) [36] to estimate the extent of occurrence (EOO) and the area of occupancy (AOO) of the species, followed by applying the IUCN Red List Categories and Criteria [37] for conservation status assessment.

4.4. Molecular Analysis

4.4.1. Sample Collection, DNA Extraction and Sequencing

Fresh leaves of Cathetus yuanjiangensis were collected from living plants in Yuanjiang County, and voucher specimens (Collection Number: Huan C. Wang et al. YJ31040 and Chao Chen YJ31054) were deposited at YUKU. The genomic DNA was extracted from fresh leaves. The short-insertion library (350 bp) was constructed and then sequenced to obtain 2 × 150 bp paired-end data by using the Illumina NovaSeq 6000 platform (Illumina, San Diego, CA, USA) at Novogene (Beijing, China), and 10 GB of raw data was obtained.

4.4.2. Plastid Genome Assembly and Annotation

The raw data for the new species were filtered through Trimmomatic v. 0.39 [41] to obtain a clean dataset. The plastid genomes were assembled using GetOrganelle v1.7.7.1 [42] with default parameters. Initially, the online program GeSeq with default parameters [43] was utilized to annotate the complete plastome. The putative start and stop codons of protein-coding genes were manually adjusted in Geneious Prime 2020.0.3, using the published plastome of Cathetus clarkei as the reference [31]. The resulting circular physical map of the plastome of C. yuanjiangensis was drawn using CPGview [44].

4.4.3. Nuclear Data Extraction

Whole nuclear ribosomal DNA repeat unit (nrDNA) comprising the complete sequence of 18S–5.8S–26S genes, as well as non-coding external and internal transcribed spacers (ETS and ITS), were assembled using the GetOrganelle v1.7.7.1 [42] with default parameters. The phytochrome C (PHYC) gene of Cathetus fasciculata (GenBank accession number: MN904262) was used as the reference genome for the PHYC assembly. We used BWA v. 0.7.17 with default parameters [45] to facilitate the reads mapping to the reference gene. SAMtools v.0.1.18 with default settings [46] converts the SAM file to BAM format while filtering out unmapped sequences and low-quality sequences. Paired mapped sequences are then extracted from the filtered BAM file and output as paired-end fastq files, with unpaired sequences and single-end sequences discarded. The extracted data were assembled into contigs using SPAdes [47]. A BLAST database is constructed from the assembly results using NCBI BLAST+ (v2.16.0), followed by blastn alignment to screen for the best-matching contig. Finally, the sequence file with the highest homology to the reference sequence is obtained.

4.4.4. Dataset and Phylogenetic Analysis

We utilize two nuclear (high-copy spacer ITS and low-copy PHYC) and three plastid (accD-psaI, trnS-trnG and matK) DNA markers and constructed phylogenetic trees using two sets of matrices with the Maximum Likelihood (ML) and Bayesian Inference (BI) methods. The three plastid DNA markers of Cathetus fasciculata and C. clarkei were extracted from the plastid genome; the ITS sequences of C. fasciculata were extracted from whole nrDNA; the rest were downloaded directly from GenBank (Table A2).

The sequences were aligned using MAFFT v.7.490 [48] and trimmed using trimAl v.1.4.1 [49], in which poorly aligned regions were removed. Then, the ITS region was concatenated with PHYC, while accD-psaI, trnS-trnG, and matK were concatenated together, resulting in the construction of two datasets (nuclear and plastid).

Taxon sampling in this study was limited by the availability of comparable molecular data. Although approximately 40 species have been described in Cathetus, only a subset is currently represented by multilocus sequences appropriate for the phylogenetic matrices used here. Consequently, the concatenated nuclear dataset included 30 sequences of Cathetus, and the concatenated plastid regions included 28 sequences. Nevertheless, our sampling covers both subgenera of Cathetus. Under these circumstances, our analyses were performed to assess the phylogenetic position of C. yuanjiangensis among the sampled taxa. For the phylogenetic analysis, we selected outgroups based on the phylogenetic tree of Phyllanthus sensu lato established by Bouman et al. [5], using Nymphanthus sootepensis (Craib) R.W.Bouman and Kirganelia glauca (Wall. ex Müll. Arg.) R.W.Bouman as outgroups.

For the concatenated nuclear dataset and plastid regions, the best-fit substitution models were identified via the Bayesian Information Criterion (BIC) using ModelFinder [50]. The maximum-likelihood tree was inferred using IQ-TREE v.1.6.12 [51], and the ultrafast bootstrap feature “-bb 1000” [52] was used to obtain branch support. The BI analysis was performed using MrBayes 3.2.2 [53], with evolutionary rate heterogeneity modeled by 4 gamma categories; two parallel runs were performed, each comprising 4 chains (1 heated and 3 cold) for 100,000,000 generations, with sampling carried out every 1000 generations. The first 25% of samples were discarded as burn-in. All the phylogenetic trees were visualized in FigTree v.1.4.4 and edited in WPS Office 12.1.0.26899.

Acknowledgments

We are grateful to Tao Chen for assistance in preparing the distribution maps. We thank the curators and the staff of the consulted herbaria for making specimens or digital information available for our study.

Appendix A

Figure A1.

Figure A1

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Schematic map of overall features of the plastid genome of Cathetus yuanjiangensis. The map contains six tracks. From the center outward, the first track shows the dispersed repeats. The dispersed repeats consist of direct (D) and Palindromic (P) repeats, connected with red and green arcs. The second track shows the long tandem repeats as short blue bars. The third track shows the short tandem repeats or microsatellite sequences as short bars with different colors. The small single-copy (SSC), inverted repeat (IRa and IRb), and large single-copy (LSC) regions are shown on the fourth track. The GC content along the genome is plotted on the fifth track. IThe genes are shown on the sixth track. The optional codon usage bias is displayed in the parenthesis after the gene name. Genes are color-coded by their functional classification. The transcription directions for the inner and outer genes are clockwise and anticlockwise, respectively. The functional classification of the genes is shown in the bottom left corner.

Table A1.

Scientific names, voucher information, and GenBank accession numbers (ITS, PHYC, accD-psaI, trnS-trnG and matK) of the specimens used in this study. A dash (–) indicates missing data.

ID Voucher ITS PHYC accD-psaI trnS-trnG matK
C. beckleri Australia, Hosking 2680 (NE) MN915861 MN904231 MN915347 MN915618 MN916127
C. chrysanthus New Caledonia, Munzinger and McPherson 796 (MO) AY936680 – – – AY936585
C. distichus USA, Hawai’i, Harold st. John 17.985 (L) MN915912 MN904276 MN915404 MN915665 MN916163
C. exilis Australia, Hunter et al. 1528 (L) MN915922 MN904283 – MN915672 MN916362
C. aff. fasciculata 1 China, Yunnan, Xishuangbanna Tropical Botanical Garden, Bouman and Yong RWB052 (HITBC) MN915840 MN904250 MN915324 MN915601 MN916144
C. aff. fasciculata 2 China, Yunnan, Xishuangbanna Tropical Botanical Garden, Bouman and Yong RWB065 (HITBC) MN915841 MN904251 MN915325 MN915602 MN916145
C. aff. fasciculata 3 China, Yunnan, Xishuangbanna Tropical Botanical Garden, Bouman and Yong RWB060 (HITBC) MN915842 MN904252 MN915326 MN915603 MN916146
C. fasciculata 1 China, Xia et al. s.n. (K) AY936684 – – – AY936589
C. fasciculata 2 China, Hong Kong, Bouman et al. RWB026 (L) MN915895 MN904262 MN915384 MN915648 MN916154
C. filicaulis Australia, Telford 13516 (NE) MN915923 MN904284 MN915415 MN915673 MN916170
C. gardnerianus Sri Lanka, Kathriarachchi et al. 42 (K) AY936694 MN904314 MN915429 MN915684 AY936598
C. glaucophyllus 1 Guinea, Van der Brugt 1156 (WAG) MN915938 MN904317 MN915432 MN915687 MN916183
C. glaucophyllus 2 Guinea, Haba 123 (WAG) MN915939 MN904318 MN915433 MN915688 MN916340
C. kerstingii 1 Guinea, Malaisse 14792 (WAG) MN915951 – MN915448 MN915702 –
C. kerstingii 2 Guinea, Darbyshire 562 (WAG) MN915950 MN905074 MN915447 MN915701 MN916189
C. myrtifolius 1 Sri Lanka; Kathriarachchi et al. 12 (K) AY936712 – – – AY936616
C. myrtifolius 2 China, Hong Kong University campus, Bouman and Liu RWB034 (L) MN915995 MN904370 MN915495 MN915736 MN916214
C. myrtifolius 3 China, Yunnan, Xishuangbanna Tropical Botanical Garden, Bouman and Yong RWB053 (HITBC) MN915996 MN904371 MN915496 MN915737 MN916215
C. myrtifolius 4 Singapore, Singapore Botanical Garden, Yu 58 (L) MN915997 MN904372 – MN915738 MN916216
C. petraeus Liberia, Blyden 1037 (WAG) MN916026 MN904397 MN915524 MN915763 MN916239
C. ussuriensis Japan, Kawakita 124 (KYO) – FJ235366 – – FJ235274
C. virgatus 1 Australia, Wrigley and Telford 46642 (K) AY936738 MN904442 MN915574 MN915807 AY936639
C. virgatus 2 China, Hong Kong, Bouman RWB069 (L) MN916074 MN904440 MN915572 MN915805 MN916276
C. virgatus 3 China, Hong Kong, Bouman RWB070 (L) MN916075 MN904441 MN915573 MN915806 MN916277
C. wheeleri Sri Lanka, Kathriarachchi et al. 33 (K) AY936740 MN904445 MN915577 MN915810 AY936641
C. beillei 1 Tanzania; Bidgood et al. 1882 (K) AY936739 – – – AY936640
C. beillei 2 Thailand, JM-40231 AB550103 – – – –
C. clarkei 1 China, Yunnan, S. X. Luo 425 (IBSC) HM106989 – – – –
C. clarkei 2 China, Yunnan, Min Fan FM2022111811 – – extracted from the plastid genome, OR683690
C. yuanjiangensis 1 China, Yunnan, Wang HuanChong et al. YJ31040 (YUKU) PZ230145 PZ225068 extracted from the assembled plastid genome, PZ210709
C. yuanjiangensis 2 China, Yunnan, Yuanjiang, Chen Chao YJ31054 (YUKU) PZ230144 PZ225069 extracted from the assembled plastid genome, PZ210710
Nymphanthus sootepensis Myanmar, Makino banical garden expedition (2015) 103753 (MBK) MN916060 MN904427 MN915559 MN915791 MN916266
Kirganelia glauca China, Hong Kong, Bouman and Liu RWB028 (L) MN915940 MN904291 MN915434 MN915689 MN916175
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Table A2.

List of genes was annotated in the chloroplast genome of Cathetus yuanjiangensis.

Category Gene Group Gene Name Number
Photosynthesis Subunits of photosystem I psaB, psaA, psaI, psaJ, psaC 5
Subunits of photosystem II psbA, psbK, psbI, psbM, psbD, psbC, psbZ, psbJ, psbL, psbF, psbE, psbB, psbT, psbN, psbH 15
Subunits of NADH dehydrogenase ndhJ, ndhK, ndhC, ndhB(2) #, ndhF, ndhD, ndhE, ndhG, ndhI, ndhA #, ndhH 12
Subunits of cytochrome b/f complex petN, petA, petL, petG, petB #, petD # 6
Large subunit of rubisco rbcL 1
Subunits of ATP synthase atpA, atpF, atpH, atpI, atpE, atpB 6
Self-replication Proteins of large ribosomal subunit rpl33, rpl20, rpl36, rpl14, rpl16 #, rpl22, rpl2(2) #, rpl23(2), rpl32 11
Proteins of small ribosomal subunit rps2, rps14, rps4, rps18, rps12(2) ##, rps11, rps8, rps3, rps19, rps7(2), rps15 13
Subunits of RNA polymerase rpoC2, rpoC1 #, rpoB, rpoA 4
Ribosomal RNAs rrn16S(2), rrn23S(2), rrn4.5S(2), rrn5S(2) 8
Transfer RNAs trnK-UUU #, trnQ-UUG, trnS-GCU, trnS-CGA #, trnR-UCU, trnC-GCA, trnD-GUC, trnY-GUA, trnE-UUC(3) #, trnT-GGU, trnS-UGA, trnG-GCC, trnM-CAU(4), trnS-GGA, trnT-UGU, trnL-UAA #, trnF-GAA, trnV-UAC #, trnW-CCA, trnP-UGG, trnL-CAA(2), trnV-GAC(2), trnA-UGC(2) #, trnR-ACG(2), trnN-GUU(2), trnL-UAG 36
Other genes Maturase matK 1
Protease clpP ## 1
Envelope membrane protein cemA 1
Acetyl-CoA carboxylase accD 1
c-type cytochrome synthesis gene ccsA 1
Conserved open reading frames ycf3 ##, ycf4, ycf2(2), ycf1(2) 6
Total 128
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#: one intron number, ##: two intron number, (n): gene copy number.

Author Contributions

Conceptualization, F.Y. and H.-C.W.; methodology, F.Y., C.C. and Z.L.; investigation, F.Y., C.C., J.-Y.W., H.F. and H.-C.W.; resources, H.-C.W.; data curation, C.C., H.F. and Z.L.; writing—original draft preparation, F.Y.; writing—review and editing, J.-Y.W. and H.-C.W.; visualization, F.Y. and C.C.; supervision, H.-C.W.; funding acquisition, H.-C.W. All authors have read and agreed to the published version of the manuscript.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Funding Statement

This work was supported by the Yunnan Provincial Wildlife Conservation Project (2025GS205Z-01) and the National Natural Science Foundation of China (31960040).

Footnotes

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Data Availability Statement

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