Camellia puhoatensis (Sect. Archecamellia – Theaceae), a new species from Vietnam

Abstract A new species of Theaceae, Camellia puhoatensis N.S. Lý, V.D. Luong, T.H. Le, D.H. Nguyen & N.D. Do, sp. nov., is described and illustrated from Nghe An Province, North Central Coastal Region, Vietnam. It is most similar to C. chrysanthoides, C. flavida and C. petelotii within sect. Archecamellia in shape and colouration of leaf, petal, ovary and glabrous stamen, but differs by its young puberulous shoot, mature leaf sparsely puberulous abaxially and leaf base rounded or broadly obtuse, petiole and pedicel puberulous, tepals 12–13, ovary and style pubescent. The comparison between the new species and C. velutina and C. dormoyana is presented. Data on distribution, ecology, phenology, use and provisional conservation assessment of the new species are given along with an illustration and a colour plate.

introduction Camellia Linnaeus (1753) is the largest genus of the family Theaceae, with recent authors recognising species between 120 (Ming and Bartholomew 2007) and 280 (Chang 1981;Gao et al. 2005), distributed widely in East and Southeast Asia, from the Himalayas east to Japan and Indonesia (Chang and Ren 1998;Ming and Bartholomew 2007). The highest species diversity is found in China and Vietnam (Chang and Ren 1998;Ming 2000;Orel and Wilson 2012b). Camellia is distinguished from other genera of Theaceae by its usually large and apically dehiscent capsules and wingless (semi-)globose or polygonal seeds with an umbilicate hilum (Ming and Bartholomew 2007). The general introduction to the genus, with particular focus on Vietnam, was given in recent publications by various authors (e.g. Orel et al. 2012Orel et al. , 2013Orel et al. , 2014aLuong et al. 2016a;Nguyen et al. 2018;Pham et al. 2019;Do et al. 2019a, b). So far, more than 75 species of Camellia have been reported in Vietnam, with many localised endemic species (e.g. Pitard 1910;Gagnepain 1941;Rosmann 1999;Tran 1998a, b;Pham 2000;Hakoda and Tran 2001;Hakoda et al. 2007;Orel 2006;Orel andWilson 2010a, b, 2012a, b;Orel and Curry 2014;Orel et al. 2012Orel et al. , 2013Orel et al. , 2014aLuong 2012, 2013;Le 2013, 2015;Luu et al. 2015Luu et al. , 2018Luong et al. 2016a, b;Le et al. 2017;Nguyen et al. 2018;Pham et al. 2019;Do et al. 2019a, b), but the actual number is expected to be higher in the near future Luong 2016, Do et al. 2019b).
During recent extensive floristic surveys in the North Central coastal region in Vietnam, several interesting species of Camellia in yellow flower were collected by one of us (N.-D. Do) and colleagues in 2018-2019 (e.g. Tran and Luong 2013;Tran and Le 2015;Luong et al. 2016a, b;Le et al. 2017;Nguyen et al. 2018;Pham et al. 2019;Do et al. 2019a, b). Critical examination of living flowers, dried specimens and comparison with type material and protologues of all related yellow Camellia in Vietnam and China (e.g. Sealy 1958;Chang 1981;Chang and Bartholomew 1984;Gao et al. 2005;Ming 2000;Ming and Bartholomew 2007;Pham 2000;Orel and Curry 2014) led to the discovery of several new taxa, two of which were recently described and named C. pukhan gensis D.N. Do, D.V. Luong, S. T. Hoang & H.T. Le and C. ngheanensis N.D. Do, V.D. Luong, N.S. Ly, T.H. Le & D.H. Nguyen (Do et al. 2019a, b), while some other collections are still awaiting description. In this paper, we describe a further new Camellia from the Pu Hoat Nature Reserve, Nghe An Province, Vietnam. The overall plant habit, somewhat ovate leaf blades, orbicular sepals and bright yellow tepal of these plants in Pu Hoat NR show similarities with C. chrysanthoides H.T. Chang, C. flavida H.T.Chang, C. petelotii (Merr.) Sealy and C. dormoyana (Pierre) Sealy (Sealy 1949(Sealy , 1958Chang 1979Chang , 1981). However, it shows significant differences in its vegetative and floral structures (see Table 1) and we describe it here as a new species to science, C. puhoatensis.

Materials and methods
The descriptions are mainly based on measurements from mature individuals of living plants in the field, supplemented by measurements from herbarium specimens. Type specimens of the most closely-related species of yellow camellias were examined from the following herbaria: DLU, HN, P, NSW and VNM (herbarium codes follow Thiers 2018). Hi-resolution digital images available were also accessed from botanical websites (e.g. https://science.mnhn.fr/, http://www.cvh.org.cn/, https://avh.ala.org.au/, https:// plants.jstor.org/). All morphological characters were described using the general terminology and standard works of Sealy (1958), Chang (1981), Chang and Bartholomew (1984), Chang and Ren (1998), Gao et al. (2005), Ming (2000) and Ming and Bartholomew (2007). The conservation status was assessed, based on field observations in accordance with the IUCN Red List Categories and Criteria version 3.1 (IUCN 2017). Diagnosis. Camellia puhoatensis is morphologically similar to C. chrysanthoides, C. fla vida and C. petelotii, but differs in having young puberulous shoots, mature leaves sparsely puberulous abaxially with leaf bases rounded or broadly obtuse, petioles and pedicels puberulous, tepals 12-13 and the ovary and styles pubescent.
Phenology. Flowering from November to January of the next year. Distribution and habitat. Camellia puhoatensis is currently found only from the type locality. It grows on moist fertile and sandy soils along mountain streams and hill slopes in evergreen broad-leaved forests in Pu Hoat Nature Reserve, Vietnam, at elevations of 270-450 m.
Provisional conservation assessment. At present, only a single population of about 300 scattered mature individuals of Camellia puhoatensis was observed in the type locality, with an estimated extent of occurrence (EOO) less than 100 km 2 and an area of occupancy (AOO) less than 1 km 2 . The population is highly threatened due to loss of habitat within its range and high market demands for wild, yellow-flowered camellias which are intensively collected for sale by local people. Therefore, C. puhoat ensis is preliminarily categorised as Critically Endangered [B1ab (i, ii, iii) + 2ab (ii, iii), D], according to the IUCN Categories and Criteria (IUCN 2017 (Sealy 1958;Chang and Bartholomew 1984;Ming 2000) and was based on the assessment of morphological characteristics. The taxo- nomic system of Sealy (1958) and Chang and Bartholomew (1984) are used to describe and determine the placement of new taxa within Camellia. These systems are the most detailed and comprehensive study of the genus and also provide the basis for our current understanding of the genus. The taxonomic system of Ming (sensu Ming and Bartholomew 2007) was used for supplementary data only as it appears to be superficially similar to the system of Sealy (Orel and Wilson 2010a). In this paper, we have followed the Sealy's (1958) taxonomic system to consider the placement of the new species within Section Archecamellia Sealy of Camellia. Morphologically, C. puhoatensis possesses a solitary or paired flowers at terminal (sometimes axillary), stout, thick and erected pedicel, 3-4 persistent bracteoles, 5 persistent sepals (undifferentiated bracteoles and sepals), large yellow flowers with 12 tepals that are inner ones basally connate and adnate to androecium, androecium free above the union with the petals or unified for some distance to form a fleshy cup, filaments glabrous, gynoecium 3(-4)-loculi, styles 3(-4) and free to the base. These characteristics are not only identical to the species of sect. Archaecamellia Sealy (sensu Sealy 1958; sensu Chang and Bartholomew 1984), but also share with species of sect. Stereocarpus which possesses 2 or 4 bracteoles (sensu Sealy 1958), terminal flowers (sensu Chang and Bartholomew 1984), stamens in 3-4 whorls, ovary with 3-5 locules (sensu Ming 2000), as well as sharing with species of sect. Chrysantha Chang, such as distinct peduncle, small floral bracteolates, yellow flowers, three carpels of gynoecium and separate styles (sensu Chang 1979). As characterized by Sealy (1958), sect. Archaecamellia shares several traits with sect. Stereocarpus. These include a solitary and erected flower at the end of the branches, persistent bracteoles and sepals, stamens united with the petals and glabrous filaments. However, traits that are distinctive to sect. Archaecamellia include (6-)11-16 indistinct bracteoles and sepals, 8-14 petals, glabrous or pubescent gynoecium and 3 or 5 free styles (vs. 2 or 4 bracteoles and 5 or 6 sepals, ca. 12 petals, glabrous gynoecium and a single style in sect. Stereocarpus). The sect. Chrysantha also shares several traits with sect. Archaecamellia in having yellow and pedicellate flowers, persistent bracteoles and sepals, glabrous or hairy filaments and gynoecium, but it can be distinguished from sect. Archaecamellia by the axillary flowers, distinct bracts and sepals and 3-5 cleft styles (Chang 1979). Section Archaecamellia is currently comprised of 19 species (Sealy 1958;Ming 2000;Orel and Wilson 2012a;Do et al. 2019a). The new species is most similar to C. chrysanthoides H.T.Chang, C. flavida H.T. Chang and C. petelotii (Merr.) Sealy in having the same plant habit, somewhat oblong leaves, yellow flowers, glabrous 3-loculed gynoecium with 3 styles free to the base. A detailed morphological comparison between C. puhoatensis and these three species is provided in the above diagnosis and in Table 1. Moreover, C. puhoatensis also resembles C. dormoyana (Pierre) Sealy of sect. Stereocarpus (Sealy 1958) and C. velutina V.T. Pham et al. of sect. Chrysantha (Pham et al. 2019) by somewhat oblong leaves, yellow flowers and glabrous stamens. However, Camellia dormoyana is easily distinguished from C. puhoatensis by having the young shoots, mature leaves and petioles all glabrous, the sessile pedicel and 5-6 bracteoles abaxially velutinous, the abaxial petals silky velutinous, the ovary being glabrous and with five locules and the styles united for their entire length and glabrous.
Similarly, C. velutina is readily distinguished from C. puhoatensis by its glabrous young shoots, mature leaves and petioles, sepals that are silky velutinous abaxially and velutinous adaxially, the 10 (occasionally 11) petals that are silky velutinous and glabrous ovary and style (see Table 1).