Rediscovery of Diospyros bambuseti (Ebenaceae) in Thailand: Emended taxonomic description, lectotypification, and phylogenetic placement Author Duangjai, Sutee 0000-0002-1490-759X Department of Forest Biology, Faculty of Forestry, Kasetsart University, Bangkok, 10900, Thailand. & fforsud @ ku. ac. th; https: // orcid. org / 0000 - 0002 - 1490 - 759 X fforsud@ku.ac.th 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 aroon5561@gmail.com Author Chalermwong, Porntawat 0000-0002-6310-4291 Surat Thani National Park and Protected Area Innovation Center, National Park Innovation Institute, Department of National Parks, Wildlife and Plant Conservation, Surat Thani, 84000, Thailand. & chalermwong _ p 58 @ hotmail. com; https: // orcid. org / 0000 - 0002 - 6310 - 4291 chalermwong_p58@hotmail.com Author Suekaew, Padungsak 0000-0003-4710-6040 Protected Area Regional Office 4 (Surat Thani), Department of National Parks, Wildlife and Plant Conservation, 84000, Thailand. & padungsak 9860 @ gmail. com; https: // orcid. org / 0000 - 0003 - 4710 - 6040 padungsak9860@gmail.com Author Suddee, Somran 0000-0003-4031-9721 Forest Herbarium (BKF), Department of National Parks, Wildlife and Plant Conservation, Bangkok, 10900, Thailand. & somrans @ hotmail. com; https: // orcid. org / 0000 - 0003 - 4031 - 9721 somrans@hotmail.com text Phytotaxa 2022 2022-04-06 542 3 271 282 http://dx.doi.org/10.11646/phytotaxa.542.3.3 journal article 53873 10.11646/phytotaxa.542.3.3 595f2403-9b45-4e4c-aae7-375126d4b938 1179-3163 6416686 Diospyros bambuseti H. R. Fletcher, Bull. Misc. Inform. Kew 1937: 387 ; Fl. Siam . En. 2: 364. 1938; Phengklai Fl. Thailand 2 (4): 290, Fig. 1 . 1981. Type:— Thailand . Sa Kaeo , Aranya Prathet , 12 May , 1930, Kerr 19325 ( lectotype designated here, BM barcode BM000884668; isolectotypes BK, E barcode E00318463, K barcode K000792557 and K001089520). Figs. 1–3 . Small to medium-sized trees, up to 20 m high (already flowering when ca. 2.5 m high), with a trunk diameter up to 60 cm ; trunk crooked with slight enlargements or buttresses at base; outer bark greyish-brown, smooth or scaly; inner bark thick, yellowish-brown; sapwood white; young branchlets green with dense brown hairs; older branchlets greyish-brown to brown, smooth to scaly; canopy dense and round. Leaves alternate; petiole 0.2–0.5 cm long, with dense brown hairs; lamina lanceolate, ovate-lanceolate to elliptic-oblong, 3.5–11 × 1.5–4.2 cm , base rounded or obtuse (rarely cuneate), apex acute or obtuse, margin entire or revolute, green on both surfaces, the lower surface slightly paler, upper surface glabrous, except the pubescent midrib, lower surface glabrescent; midrib impressed above, raised below, yellowishbrown; secondary veins 6–14 on each side, arched and anastomosing well away from the margin, conspicuous on both surfaces; tertiary veins conspicuous on both surfaces when fresh, secondary and tertiary veins hardly visible abaxially when dry, occasionally translucently dotted. Male flowers cymose, 3–4-merous, sessile. Calyx campanulate, 1–2 mm long, divided to middle, glabrescent outside, glabrous inside, slightly green. Corolla white; broadly urceolate or ovoid, 3–5 mm long, divided to middle; outside with a median line of hairs, glabrous inside. Stamens 16–20, glabrous. Rudimentary ovary glabrous. Female flowers solitary, 3–4-merous, sessile. Calyx broadly campanulate, 4–5 mm long, divided to middle, glabrescent outside, glabrous inside, slightly green. Corolla white; broadly campanulate or ovoid, 4–5 mm long, divided to middle; outside with a median line of hairs, glabrous inside. Staminodes 3–4, attached at the base of corolla-tube, glabrous. Ovary ovoid, 6–8-locular, villous; styles 3–4, ca 0.5–0.6 mm long, glabrous; stigmas bifid. Fruits green (yellowish green when mature), sessile, ellipsoid or elongated oboval in shape, 2.0–2.6 × 0.9–1.4 cm , base rounded, apex acute, nearly circular in cross section, smooth, sparsely pubescent, 6–8-locular, pericarp thin; seeds 1–2(3), 14–20 × 6–9 mm ; fruiting calyx divided to the base, glabrous on both surfaces, lobes broadly ovate with broad blunt apices, 4.5–6 × 4 mm , reflexed, not plicate nor undulate; endosperm ruminate. Vernacular name:— Maklua aran ( Sa Kaeo ); boon ( Surat Thani ). FIGURE 1. Diospyros bambuseti H.R.Fletcher. A. Habitat in May 2015. B. Stem and bark. B1. Inner bark. C. Flowering branches and leaves. D. Fresh leaves and venation. E. Abaxial surface of a dried leaf. F. Adaxial surface of a dried leaf. Photographed by S. Duangjai. FIGURE 2 . Diospyros bambuseti H.R.Fletcher. A –B. Male flowers. C–D. Female flowers. E. Young fruits. F. Mature fruits. G. Fruits and seeds. H. Seed and embryo. Photographed by S. Duangjai (A–B, E–F) and A. Sinbumroong (C–D, G–H). FIGURE 3 . Diospyros bambuseti H.R.Fletcher. A. Fruiting branch habit. B. Leaves. C. Male flowers. D. Male flowers. E. Fruits and seeds. Scale bars: A–B and E = 2 cm; C–D = 5 mm. Drawn by W. Bhuchaisri from Chalermwong 22102018 (A–B and E), Sinbumroong et al. 300520151 (C), and Sinbumroong 22052020 (E). Distribution:— Endemic to Thailand , known only from Aranya Prathet district, Sa Kaeo Province and Khian Sa district, Surat Thaini Province. FIGURE 4 . Phylogenetic trees of Diospyros and related genera based on DNA sequence data from eight plastid regions, showing the phylogenetic placement of D. bambuseti . A. The 50% majority rule tree obtained from Bayesian inference (BI) analysis. Posterior probability (PP) values> 0.50 are provided above the branches. B. Phylogram obtained from BI analysis showing only Diospyros clade XI. Coloured fonts indicate D. bambuseti and its closely related species. Habitat and Ecology:— Bamboo forest, riparian forest, ca. 50–100 m a.s.l. The D. bambuseti population in riparian forest of Khian Sa district, Surat Thani Province is dominated by Nauclea orientalis (L. 1753: 95) L. (1763: 243), Hydnocarpus castaneus Hook. f. & Thomson (1897: 197), Vatica diospyroides Symington (1938: 347) , Barringtonia acutangula subsp. spicata ( Blume 1827: 1097 ) Payens (1967: 231) , and Pongamia pinnata (L. 1753: 741) Pierre (1898: 385). FIGURE 5. Leaves, male inflorescence and flowers, and fruits of Diospyros ehretioides Wall. ex G. Don (A–C) and D . venosa Wall. ex A. DC. (D–F). Photographed by A. Teerawatananon (A and C), S. Nualngam (B), and A. Sinbumroong (D–F). Conservation status:— DD, following IUCN Standard and Petitions Committee (2019) . There are more than 500 individuals in the Khian Sa District, Surat Thaini. The population at Sa Kaeo Province remains unknown. Phenology:— Flowering in May–June and fruiting in May–October. Fruits ripen in October. Examined specimens:— THAILAND : Sa Kaeo [ Aranya Prathet , 12 May , 1930, Kerr 19325 ( lectotype BM!, isolectotypes BK!, E!, 2 shts. K!)] ; Surat Thani [ Khian Sa district , 30 May , 2015, Sinbumroong et al. 300520151 (fl.) (BK!; BKF!), ibid., Sinbumroong et al. 300520152 (fl.) (BK!; BKF!), ibid., Sinbumroong et al. 300520153 (fr.) (BK!; BKF!), ibid., 22 October , 2018, Chalermwong 22102018 (fr.) (BK!; BKF!), ibid., 22 May, 2020, Sinbumroong 22052020 (fl.) (BK!; BKF!)] . Notes:— In the original description, Fletcher (1937) stated that D . bambuseti was trimerous. However, both tri-and tetramerous flowers were found among our newly collected specimens of this species from Khian Sa, Surat Thani . Thus, the rediscovery of D . bambuseti demonstrates the necessity of further floristic studies in riparian forest along Tapi River , Surat Thani and the importance of protecting this forest area, as it harbours a population of an endemic Diospyros species .