Lithocarpus eiadthongii (Fagaceae), a new stone oak species from southern part of Thailand Author Sinbumroong, Aroon 0000-0001-8504-4106 Protected Area Regional Office 4 (Surat Thani), Department of National Parks, Wildlife and Plant Conservation, 84000, Thailand. aroon 5561 @ gmail. com; https: // orcid. org / 0000 - 0001 - 8504 - 4106 & Department of Forest Biology, Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand. aroon5561@gmail.com Author Rueangruea, Sukid Forest Herbarium (BKF), Department of National Parks, Wildlife and Plant Conservation, 61 Phahonyothin Rd., Chatuchak, Bangkok 10900, Thailand. Author Teerawatananon, Atchara Natural History Museum, National Science Museum, Technopolis, Pathum Thani 12120, Thailand. & Center for Advanced Studies in Tropical Natural Resources, Kasetsart University, Bangkok 10900, Thailand. Author Sungkaew, Sarawood Center for Advanced Studies in Tropical Natural Resources, Kasetsart University, Bangkok 10900, Thailand. & Department of Forest Biology, Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand. text Phytotaxa 2022 2022-03-22 541 1 73 78 http://dx.doi.org/10.11646/phytotaxa.541.1.7 journal article 20141 10.11646/phytotaxa.541.1.7 070f7acb-4a32-4f70-8c68-97818f692f55 1179-3163 6375259 Lithocarpus eiadthongii Sinbumr., Rueangr. & Sungkaew , sp. nov. ( Figs. 1 & 2 ) Diagnosis:— Lithocarpus eiadthongii is superficially similar to L. melataiensis , L. pusillus and L. vuquangensis . In terms of leaf characters, it may look like L. vuquangensis , but it is, however, much different from the latter in terms of fruit characters (having cupule size of 4−7 mm high by 8−13 mm across; cupule surface with (5)6−9 lamellae; nut size of 0.8−1.5 cm across; nut basal scar of 4−8 mm across in L. eiadthongii vs cupule size of ca 14 mm high by ca 18 mm across; cupule surface with 4−5 lamellae; nut size of 2.1−2.4 cm across; nut basal scar of ca 11 mm across in L. vuquangensis ). Whilst, in terms of fruit characters, it may look similar to L. melataiensis and L. pusillus , but L. eiadthongii differs from the latter two in having a stalked cupule of 3−6 mm long ( vs sessile cupule in L. melataiensis vs sessile to stalked cupule of 2−3 mm long in L. pusillus . Moreover, in terms of leaf characters, L. eiadthongii is much different from the latter two in having a leaf acumen of 3−10 cm long and leaf undersurface with sparsely white to creamy-white waxy to glabrous ( vs leaf acumen of 15−22 mm long and leaf undersurface with densely yellowish brown tomentose, sometimes with simple hairs in L. melataiensis vs leaf acumen of 10−30 mm long and leaf undersurface with densely greyish brown tomentose by adpressed, minute, stellate hairs in L. pusillus ) ( Table 1 ). Type :— THAILAND . Ranong province : Mueang Ranong district , Ngao subdistrict, Namtok Ngao National Park , hillside, UTM 47P E459665 N1090233, elev. 214 m , 4 July 2020 , Sinbumroong 04072020 ( holotype : BKF!; isotypes: BKF!, Kasetsart University, Faculty of Forestry , Bangkok , Thailand!, Natural History Museum, Thailand!) . Description:—Medium to large sized evergreen tree, 15−35 m tall, 20−85 cm in diam. at breast height; buttresses usually present, up to 2 m tall. Outer bark greyish brown or greenish grey, smooth and lenticellate, usually with superficial horizontal lines, becoming finely winding- and shallow-fissured to finely scaly. Inner bark easily detached from the sapwood, reddish brown to dark brown, surface of inner bark facing sapwood equipped with numerous longitudinal ridges resulting numerous longitudinal and slightly depressed purplish lines with 0.5−1.5 cm long on white to slightly creamy sapwood. Branchlets yellowish green in vivo and reddish brown to dark brown in sicco , grooved, sparsely covered with white wax and lenticels, becoming glabrous. Terminal buds tiny, ovoid, ca. 1 by 1 mm ; scaly, scales ovate, spirally imbricate. Stipules not seen. Leaves simple, spirally arranged along twig, not crowded near the end of each flush; blades narrowly elliptic, lanceolate-elliptic, oblong-ovate to lanceolate-ovate, (linear-elliptic in sapling stage,) thin coriaceous, rigid, 6−12.5 by 1.5−3.5 cm ; adaxially green, glabrous, dull to glossy, abaxially pale greyish to creamy green, sparsely covered with white to creamy-white wax to glabrous; base acute or cuneate to slightly attenuate, apex acute to bluntly acuminate, acumen 3−10 mm long; margin entire, sometimes slightly undulate; midrib thin, slightly raised on both surfaces; secondary veins (9−)11−13(14) pairs, thin, obscure to slightly distinct both sides, subparallel, at an angle of 50°−60°, slightly arcuating and faintly anastomosing near the margin; veinlets fine reticulated, irregular or areolate, obscure on both sides; petiole 6−10 mm long, 1.3−2 mm in diam., usually straight to slightly curved, adaxially furrowed, abaxially rounded, sparsely covered with white to creamy-white wax to glabrous. Inflorescences usually androgynous (terminal) and branched, occasionally female (subterminal) and unbranched, erect, 4−10 cm long, peduncle 1−2 mm in diam. (androgynous inflorescence) or 1.5−3 mm (female inflorescence), densely covered by creamy stellate and single hairs; bracts and bracteoles deltoid to ovate-acute, ca 0.1−0.4 mm . Male flowers solitary on the upper part of androgynous inflorescence; perianth 5−6-lobed, coriaceous, broadly ovate-acute to broadly ovate-rounded, 0.3−0.5 by 0.5−1.2 mm ; stamens 10−12; filaments 0.8−1.1 mm long, anthers 0.2−0.3 mm long; pistillode globose, 0.5−0.8 mm in diam. Female flowers solitary on the lower part of androgynous inflorescence or in clusters of 2−7 on female inflorescence; perianth 5−6-lobed, coriaceous, broadly ovate-acute to broadly ovaterounded, 0.3−0.6 by 0.3−0.7 mm ; staminodes 10−12, rudimentary; styles 3(4), conical, 0.2−0.4 mm long, erect to slightly recurved. Infructescence woody, as long as inflorescence. Ripe cupule solitary (that from female inflorescence not seen); 3−6 mm stalked, lamellate, usually set in 2−3 regular lines; deeply cup or obconical, 4−7 mm high, 8−13 mm across; densely and creamy tomentose with stellate and simple hairs, lamellate; wall woody, thin; rim thin, enclosing 1/6−1/5 part of the nut; lamellae distinct, rim entire or faintly denticulate, set in (5)6−9 regular lines. Nut obovoid or ovoid, 1.5−2.2 cm long by 0.8−1.5 cm across, greater part glabrous, only densely covered with appressed creamy stellate and single hairs upward, chocolate-brown, base slightly rotundate to rotundate-truncate, top sharply acute; scar concave, 4−8 mm in diam., 0.7−1.4 mm deep; wall bony, thin, 0.5−1 mm thick. FIGURE 1. Lithocarpus eiadthongii . A. Fruiting leafy twig; B. Androgynous inflorescence on leafy twig; C. Female flower; D. Male flower. Drawn from Sinbumroong 04072020 by A. Teerawatananon. Etymology:—The specific epithet eiadthongii is named in honour of a well-known Thai dendrologist, Associate Professor Wichan Eiadthong who specialized in many families of Thai flora including Fagaceae ( Eiadthong, 1993 ) . Vernacular:—Ko look eiad (Thai), meaning an oak tree with small fruit. Ecology and distribution:— Currently , it is only known from peninsular Thailand ; in Namtok Ngao National Park and Klong Naka Wildlife Sanctuary of Ranong province and Si Phang-nga National Park of Phangnga province . They grow in the co-dominant and intermediate layers of the evergreen forest canopy, particularly along the hillsides, between 60 m and 260 m elevation. TABLE 1. Morphological comparisons and their natural distributions of Lithocarpus eiadthongii , L. melataiensis , L. pusillus and L. vuquangensis .

Morphological traits and species distribution	L. eiadthongii	L. melataiensis (from Julia & Soepadmo, 1998 )	L. pusillus (from Soepadmo, 1970 ; Anderson 4560 (holotype: L!; isotypes: A!, K!))	L. vuquangensis (from Ngoc et al. , 2018 )
Leaf blade	Narrowly elliptic, lanceolate-elliptic, oblong-ovate to lanceolate-ovate; 6−12.5 cm long by 1.5−3.5 cm wide	Narrowly elliptic; 9−13.5 cm long by 2−3 cm wide	Narrowly elliptic or lanceolate-elliptic to lanceolate-ovate; (4−)6−10(−12.5) cm long by (1.7−)2.5−4(−5) cm wide	Narrowly elliptic to lanceolate; 7.5–11 cm long by 2.3–3.6 cm wide
Leaf apex	Acute to acuminate, acumen 3−10 mm long	Caudate or long acuminate, acumen 15−22 mm long	Acuminate-caudate, acumen 10−30 mm long	Long acuminate, acumen up to 12 mm long
Leaf blade covering	Upper surface glabrous, lower surface sparsely white to creamy-white waxy to glabrous	Upper surface sparsely appressed brownish tomentose, lower surface densely yellowish brown tomentose, sometimes with simple hairs	Upper surface glabrous, lower surface (except midrib and nerves) densely greyish brown tomentose by adpressed, minute, stellate hairs	Upper surface glabrous, lower surface white farinose
Cupule	Stalked, 3−6 mm long; usually solitary; deeply cup or obconical; 4−7 mm high by 8−13 mm across	Sessile to stalked, 2−3 mm long; solitary; cup Sessile; solitary; deeply saucer-shaped; 4−7 mm to saucer-shaped; ca 3 mm high by 8−12 mm high by 12−17 mm across across		Stalked, ca 4−6 mm long; solitary; broadly obconical to saucer-shaped; ca 14 mm high by ca 18 mm across
Cupule surface	Densely and creamy tomentose with stellate and simple hairs; lamellae (5)6−9, rim entire or faintly denticulate	Densely tomentose with stellate and simple hairs; lamellae 6−8, rim minutely denticulate	Densely greyish stellate hairy, hairs minute, adpressed; lamellae 4−5, rim entire or denticulate	Densely covered with tawny minute hairs; lamellae 4−5, rim shortly acuminate
Nut shape	Obovoid or ovoid, 1.5−2.2 cm long by 0.8−1.5 cm across, base slightly rotundate to rotundate-truncate	Conical, 1.7−2.0 cm long by 1.1−1.5 cm. across, base not applicable	Ovoid-conical, 0.8−1.5 cm long by 0.8−1.6 cm across, base rotundate	Obovoid or globose, 1.7−2.0 cm long by 2.1−2.4 cm across, base rotundate
Nut enclosure	Cupule enclosing 1/6−1/5 part of the nut	Cupule enclosing less than half of the nut	Cupule enclosing basal part of the nut	Cupule enclosing only basal to 1/4 part of the nut
Nut basal scar	Concave, 4−8 mm across, 0.7−1.4 mm deep	Concave, 7−10 mm across	Concave, 3−7 mm across	Concave, ca 11 mm across
Species distribution	Peninsular Thailand	Endemic to Borneo (Sarawak)	Borneo (Sarawak, Kalimantan, Sabah)	Vietnam (so far known only from Vu Quang National Park, Ha Tinh Province)

FIGURE 2. Lithocarpus eiadthongii . A. Habit of fruiting leafy twig (from the holotype Sinbumroong 04072020 ); B. Trunk, showing outer bark and buttresses; C. Flowering leafy twig, showing androgynous inflorescences; D. Dry and mature cupules and nuts, showing inside and outside of cupules, basal scar of the nuts and a longitudinal section of a nut. Photos by A. Sinbumroong. Conservation status:— Lithocarpus eiadthongii is, so far, known from only three populations, all of them occur in three neighboring protected areas. According to the IUCN Red List categories and criteria ( IUCN Standards and Petitions Committee, 2019 ), this plant could be assigned to a category of Vulnerable (VU) D2 based on its limited area of occupancy and the low number or known populations. However, insufficient data exists regarding its distribution, so we provisionally propose the species conservation status as Data Deficient (DD). Additional specimens examined:— Thailand . Ranong province , Suk Samran district , Naka subdistrict, Klong Naka Wildlife Sanctuary , hillside, UTM 47P E445772 N1045984, elev. 63 m , 12 May 2021 , Sinbumroong 12052021- 3 (BKF!, KUFF!, THNHM!) ; Phangnga province , Khura Buri district , Bang Wan subdistrict, Si Phang-nga National Park , evergreen forest, 47P E438646 N992049, elev. 253 m , 3 June 2021 , Sinbumroong 03062021 (BKF!, KUFF!, THNHM!) .