Camelliayangii (Theaceae), a new species of tea plants (Camellia section Thea)

Abstract

Figures

Camelliayangii D.Wei Zhao, sp. nov. A. Habit; B, C. Branchlets; D. Abaxial surface of leaf; E. Flower buds; F. Flower; G. A dissected flower without bracteoles, 1-sepals, 2-petals, 3-androecium, 4-pedicel, receptacle and gynoecium; H. Bracteoles; I. Pedicel, receptacle and gynoecium of a flower; J, K. Capsule. Scale bars: 5 cm (C); 1 cm (E, I, J, K); 2 cm (F); 2 mm (H). Photos: Zhao D.W. (A); Yang S.X. (B–K).

Illustration of Camelliayangii. A. Branchlet with flowers; B. A node of branchlet, showing the indumenta of the branchlet, leaf, and bud; C. A part of androecium and a petal; D. Pedicel, receptacle and gynoecium of a flower; E. Capsule; F. Seed. Drawn by Chen M.Q.

The Bayesian consensus tree reconstructed by the concatenated RPB2 (introns 11–15 and 23) and waxy data for Camelliasect.Thea and related species. Bayesian posterior probabilities (PP) ≥ 0.5 and Bootstrap values (BS; %) ≥ 50 are presented above or below branches as PP/BS. Branch lengths are proportional to the expected nucleotide substitutions per site. Numbers in bold indicate the samples were sequenced in this research.

Tables

Table 1.. Comparison of Camelliayangii and its similar species.

Character	C.fangchengensis	C.longissima	C.ptilophylla	C.taliensis	C.yangii
Indumentum of new branchlet	densely pubescent	glabrous	densely pubescent	glabrous	densely pubescent
Size of leaf blade	13–29 × 5.5–12.5 cm	7–20 × 3–9 cm	6.5–25 × 3–7.5 cm	7.5–15.5 × 3–6.5 cm	9–21 × 3.5–8.5 cm
Diameter of flower	2–3.5 cm	3–4.5 cm	2.5–3 cm	3–5 cm	4–5.5 cm
Length of pedicel	5–10 mm	17–40 mm	ca. 10 mm	8–15 mm	5–15 mm
Number of sepals	5	5	5	5	3
Size of sepals	2.5–3.5 × 4–5 mm	2.5–5 × 3–6 mm	3–7 × 3.5–7 mm	4–6.5 × 5.5–9 mm	8–9 × 10–13 mm
Indumentum of sepals	abaxially pubescent, adaxially glabrous	abaxially glabrous, adaxially sericeous	abaxially pubescent, adaxially glabrous	abaxially glabrous, adaxially sericeous	abaxially pubescent, adaxially sericeous
Indumentum of ovary	densely pubescent	glabrous	densely pubescent	pubescent	densely pubescent

Table 2.. Observed flowering and fruiting phases of Camelliayangii and other taxa of C.sect.Thea occurred or were planted nearby in Yunnan, China in 2023.

Taxon	Locality	Status	Phenology	Vouchers
C.crispula	Qiubei	Wild	14 November: flowering	Zhao et al. 516 (CSFI)
C.crispulavar.multiplex	Wenshan	Wild	22 November: fruiting	Zhao et al. 539–542 (CSFI)
C.gymnogyna	Pingbian	Wild	24 November: fruiting	Zhao et al. 550 (CSFI)
C.kwangsiensis	Guangnan	Wild	7 November: flowering	Zhao et al. 492(3), (4), (9), (10) (CSFI)
C.kwangsiensisvar.kwangnanica	Guangnan	Wild	7 November: flowering	Zhao et al. 492(1), (5), (6), (7), (8) (CSFI)
C.sinensisvar.assamica	Malipo	Planted	21 November: flowering	Zhao et al. 534 (CSFI)
C.sinensisvar.pubilimba	Guangnan	Planted	7 November: flowering	Zhao et al. 491 (CSFI)
C.tachangensis	Shizong	Wild	12 November: flowering	Zhao et al. 508, 509 (CSFI)
C.yangii	Malipo	Wild	25 December: flowering	Yang S.X. & Yin L. 7357–7359 (KUN)

Full text

Introduction

Tea (Camelliasinensis [L.] Kuntze) is the most widely cultivated commercial crop of Camellia L. (Theaceae). Its leaf buds, leaves, and young branches are manufactured to yield several kinds of beverages, such as black, green, and oolong tea (Zhao 2022). Tea and its relatives, the tea plants (C.sect.Thea [L.] Griff.), all can be used as beverage sources and their natural populations are the vital germplasm resources of current cultivars of tea (Zhao 2024).

Griffith (1854) established C.sect.Thea (Zhao et al. 2017; Zhao 2022). The section was subsequently revised by different taxonomists mainly based on morphological and phytochemical investigations, such as Dyer (1874), Cohen-Stuart (1916), Sealy (1958), Chang (1981a, 1984, 1998), and Ming (1992, 1999, 2000). Molecular phylogenetic analyses using nuclear DNA regions supported the monophyly of C.sect.Thea (Xiao and Parks 2003; Vijayan et al. 2009; Zhao et al. 2023). By contrast, phylogenomic analyses based on the complete plastid genome did not suggest that the samples of C.sect.Thea formed a monophyletic group (Yang et al. 2013; Yu et al. 2017; Yan et al. 2021). However, the monophyly of the section was generally supported in the phylogenomic investigations using data from transcriptomes of Camellia (Wu et al. 2022; Zan et al. 2023). Based on the phylogenetic analyses of biparentally inherited nuclear DNA rather than maternally inherited plastid DNA and morphological and phytochemical studies, Zhao (2024) revised C.sect.Thea comprised 11 natural species and seven infraspecific taxa, including a new member, C.longissima Hung T.Chang & S.Ye Liang. They all bear pedicellate flowers with 2–4 caducous bracteoles, persistent sepals, glabrous stamens, an apically 3–5-lobed style, and glabrous seeds. All these tea plants can be found in China. Three of them, including C.sinensisvar.assamica (Royle ex Hook.) Steenis, C.sinensisvar.pubilimba Hung T.Chang, and C.taliensis (W.W.Sm.) Melch. also occur in Indochina (Zhao 2024).

During several fieldworks in Yunnan, China in 2023, a special plant of Camellia was found in the forest of Malipo County. Subsequent morphological, phenological and phylogenetic analyses suggested that it was a distinct species of C.sect.Thea. The new tea plant is described below.

Materials and methods

Field investigations and sampling

Several fieldworks were undertaken to collect the specimens that bore flowers and/or fruits for the interested new species and other species of Camellia nearby. Photos of the habitat, habit, and fresh characters of the vegetative and propagative organs of the plants were taken. The flowering phases of different species were recorded. Clean and young leaves were collected and rapidly dried in silica gel, then stored at −30 °C for total DNA extraction. Voucher specimens were collected and deposited at the herbaria listed in Suppl. material 1. Samples were identified using a narrow circumscription based on Chang (1998) and the protologues.

Morphological and phylogenetic analyses

Morphological characters of the species were measured, described, and compared based on photos of living plants and specimens collected or examined at herbaria (acronyms following Thiers [2025], continuously updated) BM, CSFI, E, GXFI, GXMI, HITBC, IBK, IBSC, K, KUN, P, PE and SYS. Articles of publishing a new species in the Shenzhen Code (Turland et al. 2018) were complied with.

Total genomic DNA extraction and subsequent molecular phylogenetic analyses with three nuclear regions, including RPB2 introns 11–15 and intron 23 and waxy, were elaborated in Zhao et al. (2023). The GenBank accession numbers of DNA regions sequenced in this study are listed in Suppl. material 1.

Results

The morphology of the new species, C.yangii D.Wei Zhao, matches the synapomorphies of species in C.sect.Thea, including bearing a pedicellate flower, two caducous bracteoles, persistent sepals, an apically 3-lobed style, and glabrous seeds (Zhao 2024). The new species is morphologically similar to C.fangchengensis S.Ye Liang & Y.C.Zhong and C.ptilophylla Hung T.Chang because of the indumenta of vegetative organs. The morphological differences between C.yangii and its similar species in C.sect.Thea are listed in Table 1. Camelliayangii is characterized by bearing three sepals in the flower (Figs 1, 2), whereas other taxa in C.sect.Thea have five sepals. The new species bears the largest sepals (8–9 × 10–13 mm) in C.sect.Thea (Figs 1, 2, Table 1; Zhao 2024).

Camelliayangii D.Wei Zhao, sp. nov. A. Habit; B, C. Branchlets; D. Abaxial surface of leaf; E. Flower buds; F. Flower; G. A dissected flower without bracteoles, 1-sepals, 2-petals, 3-androecium, 4-pedicel, receptacle and gynoecium; H. Bracteoles; I. Pedicel, receptacle and gynoecium of a flower; J, K. Capsule. Scale bars: 5 cm (C); 1 cm (E, I, J, K); 2 cm (F); 2 mm (H). Photos: Zhao D.W. (A); Yang S.X. (B–K).

Illustration of Camelliayangii. A. Branchlet with flowers; B. A node of branchlet, showing the indumenta of the branchlet, leaf, and bud; C. A part of androecium and a petal; D. Pedicel, receptacle and gynoecium of a flower; E. Capsule; F. Seed. Drawn by Chen M.Q.

The natural individuals of C.yangii in Malipo County that were found all bore flower buds on 21 November 2023 (Yang S.X. et al. 7312–7315 at KUN, Zhao D.W. et al. 536[1]–[5] at CSFI), while other taxa of C.sect.Thea that occurred or were planted nearby were flowering or had immature fruits as shown in Table 2. Camelliayangii seems to be flowering about one month later than other tea plants (Table 2).

The DNA sequences of nuclear RPB2 (introns 11–15 and 23) and waxy regions of nine samples, representing eight species in C.sect.Thea, were sequenced in this research (Fig. 3, Suppl. material 1). They and the DNA sequences of 45 samples reported in Zhao et al. (2023) were used to reconstruct a phylogenetic tree of Camellia shown in Fig. 3. All 18 samples of C.sect.Thea form a monophyletic group with strong support (Bayesian posterior probability [PP] = 1, Bootstrap [BS, %] = 99). Two samples of C.yangii form a strong supported clade (PP = 1, BS = 100) and are nested in the supported monophyletic group (PP = 1, BS = 95) with C.longissima and C.taliensis. It suggests that the new species, C.yangii, is a member of C.sect.Thea and its phylogenetically closely related species are C.longissima and C.taliensis (Fig. 3). Therefore, the latter two are listed in Table 1 to demonstrate the morphological differences between C.yangii and them.

The Bayesian consensus tree reconstructed by the concatenated RPB2 (introns 11–15 and 23) and waxy data for Camelliasect.Thea and related species. Bayesian posterior probabilities (PP) ≥ 0.5 and Bootstrap values (BS; %) ≥ 50 are presented above or below branches as PP/BS. Branch lengths are proportional to the expected nucleotide substitutions per site. Numbers in bold indicate the samples were sequenced in this research.

Discussion

Many recognized species of C.sect.Thea were described in 1981 and 1984 by Hung T.Chang (Zhao 2024). Except for the basionym of the infraspecific taxa C.tachangensisF.C. Zhangvar.remotiserrata (Hung T.Chang, H.S.Wang & P.S.Wang) T.L.Ming, C.remotiserrata Hung T.Chang, H.S.Wang & P.S.Wang that was published in 1990, C.yangii is the only new species of natural tea plants described after 40 years. The total number of taxa of C.sect.Thea in the world reaches 12 species and seven infraspecific taxa, and China harbors all of them.

As a supported member of C.sect.Thea (Fig. 3), C.yangii may be the hairiest species of tea plants. It is unique in Camellia by bearing three large sepals in the flower, whereas other species of the genus generally bear five sepals (Table 1). Camelliayangii and its morphologically closely related species, C.fangchengensis and C.ptilophylla, are nested in the different supported clades within C.sect.Thea (Fig. 3). Meanwhile, the new species can be easily distinguished from its phylogenetically closely related plants, C.longissima and C.taliensis, by its hairy vegetative organs (vs. generally glabrous for the latter two) (Figs 1, 2, Table 1). It would be unreasonable to infer the phylogenetic relationships among tea plants solely based on the variation of morphological characters as Chang (1981b) and Ming (2000) had done.

The flowering phase of C.yangii is later than those of other tea plants nearby (Table 2). The distinct flowering periods may not suggest that the new species can naturally hybridize with other taxa of C.sect.Thea, which will support its novelty based on the biological species concept (Butlin and Stankowski 2020). Together with the morphological (Table 1) and phylogenetic (Fig. 3) analyses presented above based on the phenetic species concept (Sokal and Crovello 1970) and phylogenetic species concept (Mishler and Brandon 1987), respectively, it is reasonable to conclude that C.yangii is a new species of C.sect.Thea.

Camelliayangii has a red or purplish red and densely pubescent terminal bud (Fig. 1C, E), which can be suggested as a rare germplasm resource of tea plants based on the Chinese Agricultural Standard (NY/T 2031-2011). However, the top priority for the new species should be conservation. Camelliayangii is only known from a single population with fewer than 10 individuals in the tropical montane forest. It is extremely vulnerable to overexploitation or deforestation. Therefore, its detailed locality is absent here for conservation reasons. Further field surveys and ex-situ asexual propagations are urgently needed for C.yangii to avoid extinction.

Taxonomic treatment

Camellia

yangii

Taxon classificationPlantaeEricalesTheaceae



D.Wei Zhao sp. nov.

3C9435AB-4CB2-5BB5-B1C2-07E221589DB8

urn:lsid:ipni.org:names:77363261-1

Type material.

Holotype: China • Yunnan: Malipo, in evergreen montane forest, 858 m, 25 December 2023, Yang S.X. & Yin L. 7357 (holotype: KUN 1628256!; isotypes: CSFI!, KUN 1628257!, KUN 1628258!)

Diagnosis.

Similar to C.fangchengensis and C.ptilophylla by the densely pubescent new branchlets, abaxial surface of leaves and pedicel, but differs from them in bearing a larger flower (4–5.5 cm in diam. vs. 2–3.5 cm in diam.), less (3 vs. 5) but larger (8–9 × 10–13 mm vs. 2.5–7 × 3.5–7 mm) sepals, and sericeous (vs. glabrous) adaxial surface of the sepals (Table 1).

Description.

Evergreen shrubs or trees, 5–8 m tall. Bark grayish yellow. New branchlets densely pubescent, terminal buds red or purplish red, densely pubescent. Petioles 3–5 mm long, densely pubescent; leaf blades elliptic, oblong, or obovate, 9–21 × 3.5–8.5 cm, coriaceous, abaxially yellowish green, densely pubescent, adaxially dark green, glabrous or puberulous along midrib at base, midrib and secondary veins abaxially elevated and adaxially impressed, secondary veins 10–13 pairs, base cuneate, margin serrulate, apex acuminate. Flowers axillary, solitary or paired, 4–5.5 cm in diam. Pedicel 5–15 mm long, densely pubescent. Bracteoles 2, caducous, ovate, 2–3 × 2–2.5 mm, abaxially pubescent, adaxially glabrous. Sepals 3, persistent, suborbicular, 8–9 × 10–13 mm, abaxially pubescent, adaxially sericeous, margin ciliolate. Petals 7–8 in 1–2 whorls, white, or the outmost petal green at apex, elliptic to obovate, 15–35 × 15–25 mm, outer petals pubescent or puberulous on both surfaces, inner petals puberulous at base or glabrous on both surfaces, apex obtuse to rounded, inner 4–5 petals basally adnate to filament whorl for 2–4 mm. Stamens numerous, 20–25 mm long; filaments white or slightly pink, glabrous, outer filaments basally connate for 3–5 mm. Ovary globose to ovoid, densely pubescent. Styles 1, 18–22 mm long, gradually becoming glabrous upwards, apically 3-lobed for 5–8 mm. Capsule tri-coccal, ca. 3.5 cm in diam., ca. 2 cm in height, 3-loculed with 1 seed per locule; pericarp 1–2 mm thick. Seeds fuscous, globose, ca. 1.5 cm in diam., glabrous, Figs 1, 2.

Phenology.

Flowering December, fruiting August–September (Table 2).

Paratypes.

China. • Yunnan: Malipo County, in evergreen montane forest, 858 m, August 2023, Yang S.X. & Xiao B. 7122 (KUN); same place, 21 November 2023, Yang S.X. et al. 7312–7315 (KUN, equal to Zhao D.W. et al. 536[1]–[4] at CSFI, respectively), Zhao D.W. et al. 536(5) (CSFI); same place, 25 December 2023, Yang S.X. & Yin L. 7358 (KUN), 7359 (KUN).

Distribution and habitat.

Camelliayangii is endemic to the tropical evergreen montane forest in Malipo County.

Etymology.

Camelliayangii is named after the leading collector of its type, Dr. Shixiong Yang, an expert of the family Theaceae at Kunming Institute of Botany, Chinese Academy of Sciences. The Chinese name of C.yangii is proposed as ”三萼茶” because it bears three sepals in the flower.

Supplementary Material

XML Treatment for Camellia yangii