﻿Taxonomic revision of Camellia (Theaceae) in Thailand

﻿Abstract Natural plants of Camellia (Theaceae) in Thailand are taxonomically revised with a key, a distribution map, descriptions, specimens examined, and figures of living plants and/or dry specimens. Nine taxa comprising seven species and two varieties are recognized, including C.caudata, C.connata, C.furfuracea, C.kissi, C.kissivar.confusa, C.laotica, C.sinensisvar.assamica, C.suddeeana, and C.taliensis. Camelliacaudata and C.laotica are new records to Thailand, and C.connata and C.suddeeana are endemic to the country. Formerly recorded C.pleurocarpa and C.tenii are excluded from Thai flora because of misidentification, and C.oleifera and C.sinensis are merely cultivated in the country. Morphological descriptions of C.connata and C.laotica are improved based on additional collections examined.


Material and methods
Morphological characters were described based on living plants, herbarium specimens or their images from BK, BKF, BM, C, CMUB, E, GXMI, HITBC, IBK, IBSC, K, KKU, KUN, L, MO, NSW, P, PE, PNH, QBG, SING, SYS, and TCD (acronyms following Thiers 2024, continuously updated).Geographic distribution data were retrieved from the specimen records and mapped using ArcMap 10.7 (ArcGIS, ESRI) and optimized in Adobe Illustrator CS3.All photos of dry specimens and living plants in the figures were taken and adapted by the author.

Key to taxa of
Phenology.Flowering October-December, fruiting March-December.Distribution and habitat.Camellia caudata occurs in semi-evergreen, evergreen and deciduous montane forests at the elevations of 500-2000 m in China, India, Laos, Myanmar, Nepal, Thailand (Fig. 2), and Vietnam.
Notes.Gagnepain (1942) described the species based on three gatherings, including Poilane 13268, 13693 and 13743. Sealy (1958) suggested that Poilane 13268 and 13693 represented C. laotica whereas Poilane 13743 was a distinct species, which was subsequently given a name, C. sealyana T.L. Ming by Ming (1999).Sealy (1958) and Ming (2000) supplied a short description of C. laotica, without the characters of flowers, based on two gatherings (Poilane 13268 & 13693) in Laos.I add an account of flowers and provide a detailed description above.Notes.The nomenclature of C. sinensis var.assamica has been clarified in recent studies (Zhao et al. 2017b;Mabberley 2021; a review in Chinese see Zhao 2022a).Thea assamica was not validly published in Masters (1844) but later validated in Hooker (1847).Steenis (1949), rather than Kitamura (1950), firstly proposed the name at new rank, C. sinensis var.assamica.Zhao et al. (2017b) provided a detailed description of Assam tea, which is supplied above with adjustments to meet the requirements of a taxonomic revision here (Maxted 1992).
Phenology.Flowering October-November, fruiting April-July.Distribution and habitat.Camellia suddeeana is native to Thailand (Fig. 2) and occurs in the evergreen or deciduous forests at the elevations of 250-1200 m.
Phenology.Flowering October-February, fruiting April-November.Distribution and habitat.Camellia taliensis occurs in the montane evergreen forest at the elevations of 1100-2750 m in China, Myanmar and Thailand (Fig. 2).
Additional specimens examined.Notes.Besides Assam tea, C. taliensis is another tea source plant that occurs in Thailand.Ming (1992) recognized C. irrawadiensis as a heterotypic synonym of C. taliensis.Chang et al. (1996) disagreed with Ming (1992) and suggested that C. irrawadiensis could be distinguished from C. taliensis by its abaxially punctate (vs.glabrous) and caffeine-free (vs.present) leaves, shorter pedicel (7-8 mm vs. 12-14 mm), larger sepals (5-7 mm vs. 2-4 mm) and smaller flowers (4 cm vs. 5-6 cm in diam.).Ming (2000) trivialized the differences and retained C. irrawadiensis in the synonymy of C. taliensis.The morphological differences between them listed in Chang et al. (1996) are, however, either inaccurate (e.g., the leaves of C. irrawadiensis are not abaxially punctate) or so trivial and overlapped (e.g., the size of pedicel, sepals and flowers) so that should be treated as an infraspecific variation.The claim of caffeine-free for C. irrawadiensis in Chang et al. (1996) was referred to Sealy's (1958: 127) report. Sealy (1958) wrote that "…Dr.E.A.H. Roberts and Dr. D.J. Wood (both of the Indian Tea Association) tell me that chemically it [C.irrawadiensis] is clearly distinct from both, notably in that it does not contain caffeine."Nevertheless, Nagata and Sakai (1985) analysed two samples of C. irrawadiensis and found that they contained 0.02% and less than 0.01% caffeine, whereas the content of caffeine in C. taliensis was 2.28%.However, the variation of chemical contents may be common in the plants of C. sect.Thea (L.) Griff.For instance, Ye et al. (1997) investigated 22 samples of C. ptilophylla Hung T. Chang and suggested that all individuals contained 0.57%-6.84%theobromine; and 18 of the samples were caffeine-free, while the remaining contained 3.02%-4.94%caffeine.Therefore, the single difference of the content of caffeine may be insufficient to warrant separation of C. irrawadiensis from C. taliensis at specific rank, and Ming's (2000) treatment of them is followed here.Keng (1972: 146) listed a single collection, Smitinand 4331A at BKF (Fig. 10A, B), under C. pleurocarpa in "Flora of Thailand".However, the collection actually represents C. taliensis.Camellia pleurocarpa is native to Vietnam and bears an abaxially punctate leaf, 5-8 persistent bracteoles, abaxially sericeous perianth and glabrous ovary, whereas C. taliensis has a glabrous leaf, 2-4 caducous bracteoles, abaxially glabrous perianth and pubescent ovary.

Discussion
Among nine taxa-seven species and two varieties-of Camellia in Thailand, only two species are endemic to the country: C. connata and C. suddeeana.As stated above, C. pleurocarpa and C. tenii in Keng's (1972) account of Camellia are excluded from the flora of Thailand.The former was a misidentification of C. taliensis and the latter was frequently used to indicate C. suddeeana.Camellia thailandica was described based on a specimen collected from Thailand (Chang and Ren 1991); it is, however, a heterotypic synonym of C. kissi (Zhao 2022c).Camellia oleifera C. Abel listed in Smitinand (1975) is actually C. kissi and the former is absent in the natural flora of Thailand.Camellia sinensis provided in Gardner et al. (2000) is merely cultivated in Thailand.
Most taxa of Camellia occur in northern and north-eastern Thailand (Fig. 2).This region geographically nears the current diversity centre of the genussouthern and south-western China and northern Vietnam (Chang 1981;Ming 2000).However, previous specimens were intensively collected from several provinces such as Chiang Mai, Loei, Mae Hong Son, Phayao, and Phitsanulok.Some under-collected gaps in the mountains of Chiang Rai, Mukdahan, Nan, and Nong Bua Lamphu could be searched in future to comprehensively understand the diversity of Camellia in Thailand (Fig. 2).

Figure 1 .
Figure 1.Camellia caudata A canopy of a tree B branch C flower D petals and androecia E a dissected flower F gynoecium and pedicel.Scale bars: 5 cm (B); 1 cm (C, E); 5 mm (F).The minimum graduation of the ruler in D indicates 1 mm.

Figure 3 .
Figure 3. Camellia connata A habit B branchlets C a branch with an immature fruit D, E flowers F a dissected flower without corolla G a fruit and seeds.Scale bars: 5 cm (B); 2 cm (C); 5 mm (D, F); 1 cm (E).The minimum graduation of the ruler in G indicates 1 mm.

Figure 4 .
Figure 4. Dry specimens of Camellia furfuracea, Smitinand 12023 at BKF A specimen sheet B, C flower fragments D a part of pericarp along a branchlet bearing a pedicel and gynoecium remains E a broken seed.The minimum graduation of the rulers represents 1 mm.

Figure 6 .
Figure 6.Camellia kissi var.confusa A habitat B branchlets with flowers, flower buds and caducous fruits C, D branchlet with flower E a pedicel and gynoecium.Scale bars: 2 cm (D); 1 cm (E).The minimum graduation of the rulers in B, C represents 1 mm.

Figure 7 .
Figure 7. Dry specimens of Camellia laotica, Wongprasert s.n. at BKF A specimen sheet B branchlet with flower buds C a flower bud D a flower E, F flower fragments showing sepals and gynoecia.Scale bars: 5 mm (C, D); 3 mm (E, F).The minimum graduation of the rulers in A, B represents 1 mm.

Figure 8 .
Figure 8. Camellia sinensis var.assamica A habitat B branchlets with flowers and flower buds, adaxial surface of leaves C branchlets with flower and fruit, abaxial surface of leaves D a dissected flower E a flower without petals, androecium and a half sepal.Scale bars: 3 cm (B); 5 mm (E).The minimum graduation of the rulers in C, D represents 1 mm.

Figure 9 .
Figure 9. Dry specimens of Camellia suddeeana, Pooma et al. 7333 at BKF A specimen sheet B flower fragments C fruits and seed D calyx and gynoecium remains.The minimum graduation of the rulers in А-C represents 1 mm.

Figure 10 .
Figure 10.Camellia taliensis A, B dry specimens of Smitinand 4331A at BKF C branchlet with flower D a dissected flower E branchlet with immature fruit.Scale bars: 3 cm (C); 2 cm (D, E).The minimum graduation of the rulers in A, B represents 1 mm.

2. Camellia connata (Craib) Craib, Fl. Siam. 1(1): 131. 1925.
view and treat C. triantha as a heterotypic synonym of C. caudata.Camellia caudata is a new record to Thailand.It generally occurs in the montane forests at elevations of 900-1700 m of Northern Thailand.The species is one of several camellias that are widely distributed in Indochina, along with Assam tea, C. furfuracea and C. kissi.Kerr A.F.G. collected specimens of C. caudata in 1921 (Kerr 5041 at BK, BM, K and L).The specimens were, however, misidentified as C. connata by Keng H. in 1970 as shown on the sheet conserved at BM. Camellia caudata can be distinguished from C. connata by its basally connate styles whereas the latter bears distinct styles.