Psydrax merrillii (Rubiaceae), a new combination for a Polynesian tree species

Psydrax merrillii (Rubiaceae), a new combination for a Polynesian tree species Author: Mouly, Arnaud Source: Candollea, 79(2) : 295-298 Published By: The Conservatory and Botanical Garden of the City of Geneva (CJBG) URL: https://doi.org/10.15553/c2024v792a6 BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Complete website, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/terms-of-use. Usage of BioOne Complete content is strictly limited to personal, educational, and non - commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. Downloaded From: https://bioone.org/journals/Candollea on 15 Jan 2025 Terms of Use: https://bioone.org/terms-of-use Address of the author: Université de Franche-Comté, UMR CNRS 6249 Chrono-Environnement, 16 route de Gray, 25030 Besançon cedex, France. E-mail: [email protected] Psydrax merrillii (Rubiaceae), a new combination for a Polynesian tree species Arnaud Mouly Abstract MOULY, A. (2024). Psydrax merrillii (Rubiaceae), a new combination for a Polynesian tree species. Candollea 79: 295 – 298. In English, English abstract. DOI: http://dx.doi.org/10.15553/c2024v792a6 Canthium merrillii (Setch.) Christoph. is a tree restricted to the Polynesian archipelagos of Samoa, Tonga, and Wallis and Futuna. The paleotropical genus Psydrax Gaertn., which belongs to the tribe Vanguerieae of the family Rubiaceae, comprises unarmed shrubs bearing stamens with anthers reflexed on the filaments, whereas the species of the genus Canthium Lam. are characterized by being spinescent shrubs. Canthium merrillii (Setch.) Christoph. is therefore transferred to Psydrax based on the absence of spines. A description and an illustration of the species are provided. Keywords RUBIACEAE – Psydrax – Polynesia – New combination – Taxonomy Submitted on June 16, 2024 – Accepted on October 21, 2024 – First published online on November 20, 2024 issn : 0373-2967 (print), 2235-3658 (online) – Published by the Conservatoire et Jardin botaniques de Genève Open access article under Creative Commons Attribution Licence (CCBY4.0) Downloaded From: https://bioone.org/journals/Candollea on 15 Jan 2025 Terms of Use: https://bioone.org/terms-of-use Introduction Canthium merrillii (Setch.) Christoph. (Rubiaceae, Vanguerieae), originally described as Plectronia merrillii Setch. (Setchell, 1924), is a tree up to 15m high restricted to the Polynesian archipelagos of Samoa, Tonga, and Wallis and Futuna, where it thrives in dry littoral forests to cloud forests from see level to 700m of elevation. Canthium Lam. is a genus characterized by its spinescent habit (Lantz &Bremer, 2004), mainly occurring in continental and insular tropical Asia and East Tropical Africa. In contrast, the species belonging to Psydrax Gaertn. are unarmed and have stamens with anthers reflexed on the filaments. Canthium merrillii is a completely unarmed tree displaying stamens as mentioned for Psydrax. Moreover, the species shows further typical characters of the Pacific Psydrax: corymbiform inflorescence, style ended in a stylar head complex, and fruits with verrucose pyrenes compressed at the insertion of the hilum (Meyer, 2017). Whistler (2004) already made the combination in the genus Psydrax, cited the basionym and its author but without reference to its place of valid publication, which renders it not validly published under ICN Art.41.5 (Turland et al., 2018). The valid combination is made below by giving a full and direct reference to the place of valid publication of the basionym. Materials and methods This contribution is mainly based on the revision of digital images of specimens kept at UC, especially those belonging to Setchell’s herbarium. Collections from NOU and P were also studied, as well as digital images of specimens from AK, BISH, K, and US. New combination Psydrax merrillii (Setch.) Whistler ex Mouly, comb. nov. (Fig.1). Plectronia merrillii Setch. in Pap. Dept. Marine Biol. Carnegie Inst. Wash. 20: 49. 1924. Canthium merrillii (Setch.) Christoph. in Bull. Bernice P.Bishop Mus. 128: 201. 1935. Holotypus: American Samoa. Tutuila Island: Tutuila, fl., III.1922, Setchell [leg. Babcock &Sütupe] 423 (UC[UC220154] image!; iso-: UC[UC220155, UC469852] image!). – Psydrax merrillii (Setch.) Whistler, Rainforest Trees Samoa: 143. 2004 [comb. inval.]. Tree, up to 15m high, branches cylindrical to laterally compressed, sometimes subquadrangular, unarmed, glabrous; bark brown-reddish then grey. Stipules 4.5 – 5.5×3.5 – 4mm, triangular, connate at base, flat or slightly to deeply awned, persistent on young shoots. Leaves opposite, slightly coriaceous; lamina 8 – 16(– 20)×5 – 11(– 12)cm, elliptic-ovate, base rounded to cuneate, apex obtuse, minutely mucronate; secondary nerves 5 – 7, slightly prominent underneath, tertiary nerves visible; domatia common, pocket-like, at the axil of secondary or tertiary nerves; petiole 0.9 – 1.3cm long. Inflorescences 3 – 4×3 – 4cm, axillary, paired at nodes, corymbiform, 15 – 30 flowers, axes thin and straight, topped by short navicular bracts, solitary or in pairs. Flowers hermaphroditic, fragrant; pedicel 2 – 8mm long; hypanthium c.2mm in diam., turbinate, glabrous; calyx 5-lobed, glabrous outside, tube 0.4 – 0.8mm long, lobes 0.5mm long, triangular with obtuse apex; corolla cylindrical to campanulate, 5-lobed, pure white, turning yellow as it ages, tube 4 – 4.5×1.8 – 2.5mm, mouth with a ring of moniliform trichomes, lobes 3.5 – 4mm long, triangularlanceolate, reflexed, thick, margin slightly involute dorsally, papillose internally; stamens inserted at the corolla-lobes sinuses, exserted, filament 1.5 – 2mm long, anthers 2.5 – 3mm long, oblong, attached medio-basally and dorsally, reflexed; style elongated, 8 – 9mm long, stigmatic head 1.5 – 2mm long, cylindrical-ovoid, papillose; ovary bilocular, a single ovule per locule. Fruits 8 – 11mm in diam., 3.5 – 4mm thick, discoid, dark green to black when mature and fleshy in vivo, verrucose in sicco; pyrenes 2, c.8 – 9.5mm long, subcylindrical, thick, verrucose, crescent moon shaped. Seeds c.7mm long. Distribution and ecology. – The plant is restricted to Upolu and Savai’i in Samoa, Tutuila in American Samoa, Tafahi in Tonga, and Futuna in Wallis and Futuna. It thrives from the dry littoral forests near the coast to the cloud forests at elevations of 5 to 700m. Additional specimens examined. – American Samoa. Tutuila Island: Pago Pago, 426m, 18.III.1930, Diefenderfer 13 (BISH); s.l., VI – VII.1920, Setchell [leg. Sütupe] 518 (UC[UC215601]); West of Aoloaufou, 300m, 1.X.1976, Whistler 3672 (US). Samoa. Savai’i Island: Gataivai (inland 1 mile), 50m, 20.VIII.1968, Bristol 2269 (BISH); Taga, 5m, 6.X.1931, Christophersen 2825 (BISH, P, US), 2835 (BISH); Salailua-Lataitai, 10m, 19.X.1931, Christophersen 2860 (BISH); ibid., 17.IX.1931, Christophersen &Hume 2619 (BISH, P, US); Asau, just east of the Potlatch Lumber Mill, 20m, 11.III.1974, Whistler 1787 (BISH). Upolu Island: Ridge above Malololelei, 700m, 14.VIII.1929, Christophersen 242 (BISH); Vaea, 350m, 28.VIII.1929, Christophersen 459 (BISH, P, US); near Afulilo waterfall in the Le Mafa area, 350m, 11.II.1974, Whitsler 1571 (US); Ridge South of Mount Fao, 400m, 2.I.1976, Whistler 3241 (US). Tonga. Tafahi Island: s.l., 530 – 540m, 25.VII.1978, Buelow 1176 (AK); summit of the island, 19.XI.1987, Whistler 6255 (US); between Vai Kona and Vai Langita, 26.XI.1987, Whistler 6366 (US). Wallis and Futuna. Futuna Island: Nuku, Singave, 35m, 1.VII.1974, Kirch s.n. (BISH); Nuku, Singave, along ridge leading to Osiiti, 30 – 40m, 19.VII.1974, Kirch 160 (BISH); Mont Puke, 14.XI.2008, Munzinger et al. 5302 (K, NOU, P). 296 – A new combination in Psydrax (Rubiaceae) Candollea 79, 2024 Downloaded From: https://bioone.org/journals/Candollea on 15 Jan 2025 Terms of Use: https://bioone.org/terms-of-use Candollea 79, 2024 A new combination in Psydrax (Rubiaceae) – 297 Fig.1. – Psydrax merrillii (Setch.) Whistler ex Mouly. A.Flowering branch; B.Stipules; C.Flower in longitudinal section; D.Detail of fruiting branch; E.Fruit in lateral view. [Setchell 423, UC] [Drawing: A.Mouly] A B DE C 2 cm 2mm 1mm 2cm 5mm Downloaded From: https://bioone.org/journals/Candollea on 15 Jan 2025 Terms of Use: https://bioone.org/terms-of-use Acknowledgements The author thanks Ana Penny at the University and Jepson Herbaria, University of California, Berkeley for providing digitized specimens. References Lantz, H. &B.Bremer (2004). Phylogeny inferred from morphology and DNA data: characterizing well-supported groups in Vanguerieae (Rubiaceae). Bot. J. Linn. Soc. 146: 257 – 283. Meyer, J.-Y. (2017). Guide des plantes de Wallis et Futuna. Au Vent des Iles, Pirae, Tahiti. Setchell, W.A. (1924). American Samoa: Part I. Vegetation of Tutulia Island. Pap. Dept. Marine Biol. Carnegie Inst. Wash. 314: 1 – 175. Turland, N.J., J.H.Wiersema, F.R.Barrie, W.Greuter, D.L.Hawksworth, P.S.Herendeen, S.Knapp, W.-H.Kusber, D.-Z.Li, K.Marhold, T.W.May, J.McNeill, A.M.Monro, J.Prado, M.J.Price &G.F.Smith (2018). International Code of Nomenclature for algae, fungi, and plants (Shenzhen Code) adopted by the Nineteenth International Botanical Congress Shenzhen, China, July 2017. Regnum Veg. 159. Whistler, W.A. (2004). Rainforest trees of Samoa. A guide to the common native and naturalized lowland and foothill forest trees of the Samoan Archipelago. Isle Botanica, Hawaii. 298 – A new combination in Psydrax (Rubiaceae) Candollea 79, 2024 Downloaded From: https://bioone.org/journals/Candollea on 15 Jan 2025 Terms of Use: https://bioone.org/terms-of-use