Research Article |
Corresponding author: Gildas Gâteblé ( gildas.gateble@inrae.fr ) Academic editor: Alan Paton
© 2019 Gildas Gâteblé, Laurence Ramon, Jean-François Butaud.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Gâteblé G, Ramon L, Butaud J-F (2019) A new coastal species of Pseuderanthemum (Acanthaceae) from Loyalty Islands (New Caledonia) and Vanuatu with notes on P. carruthersii. PhytoKeys 128: 73-84. https://doi.org/10.3897/phytokeys.128.36325
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When dealing with the taxonomy of Pacific coastal species within the region of New Caledonia and Vanuatu, one should examine all names published in Australasia and other Pacific islands. When the putative new species is also closely related to a highly praised ornamental species with many cultigens and with many old horticultural names, the task becomes more arduous. This is the case for the new species we describe as Pseuderanthemum melanesicum Gâteblé, Ramon & Butaud, which is closely related to the now pantropical cultivated species P. carruthersii (Seem.) Guillaumin s.l. Compared to P. carruthersii, P. melanesicum has carnose and shiny leaves, pedicels and sepals covered with glandular hairs, a short and enlarged corolla tube and can produce fertile capsules. The new species is a coastal taxon occurring naturally in the Melanesian archipelagos of New Caledonia and Vanuatu. This species seems uncommon in the Loyalty Islands but more common in the archipelago of Vanuatu and we propose it as Critically Endangered in New Caledonia, Vulnerable in Vanuatu and Least Concern when the IUCN evaluation is done globally.
Acanthaceae, New Caledonia, new species, Pseuderanthemum, taxonomy, Vanuatu
The Pacific and Malesian taxa of Acanthaceae Juss. are in need of a broad taxonomic revision and especially those of Pseuderanthemum Radlk. (
Some recent fieldwork and specimen collection conducted by the authors in the New Caledonian Loyalty islands (Lifou and Maré) and in Vanuatu led us to think that a taxon was missing in
Most, if not all, published names of Pseuderanthemum and Eranthemum L. including some names in Anthacanthus Nees, Chrestienia Montrouz., Graptophyllum Nees, Justicia L., Pachystachys Nees, Ruspolia Lindau and Siphoneranthemum Kuntze said to be occurring in, or coming from, the central Indo-Pacific region were retrieved using
From our bibliographic and type specimen image searches for about 100 Pseuderanthemum s.l. names in the region, it appears that the new species could only be confused with P. carruthersii (Seem.) Guillaumin. This latter species is, however, quite variable morphologically and widespread in cultivation throughout the tropics. In the tropics and in the Southwestern Pacific, especially Vanuatu and New Caledonia, P. carruthersii s.l. is a common garden ornamental showing a great morphological variability, especially in leaf size, shape and color. Like many other plants with variegated or colored leaves [e.g. Abelmoschus manihot (L.) Medik, Acalypha wilkesiana Müll.Arg., Codiaeum variegatum (L.) Rumph. ex A.Juss., Cordyline fruticosa (L.) A.Chev., Dendrolobium umbellatum (L.) Benth., Graptophyllum pictum (L.) Griff., Hibiscus rosa-sinensis L. s.l., Pandanus tectorius Parkinson ex Du Roi, Plectranthus scutellarioides (L.) R.Br., Polyscias guilfoylei (W.Bull) L.H.Bailey and P. scutellaria (Burm.f.) Fosberg], we believe that Pseuderanthemum carruthersii s.l. was selected and moved around during the migrations and peopling of the Melanesian islands well before European arrival in the region (
Pseuderanthemum carruthersii was originally described by
Since P. carruthersii is a variable species and a highly regarded ornamental plant; it has been introduced multiple times from various sources and cultivated in European nurseries especially during the second half of the nineteen century. This has resulted in a plethora of names under Eranthemum, many of them being published in horticultural magazines several times with different authorships and, later on, combined or not under Pseuderanthemum and Siphoneranthemum by taxonomists. For most of the names, there is no herbarium specimen, the diagnosis is often short and/or incomplete and almost no lectotypification work has been done. It is not our intention to deal with the lectotypification and formal synonymization of all the names. Several authors have dealt, though incompletely, with the synonymization at the species or variety levels (see
Among all the names published so far, two are of particular interest for this work. The first one is the recently lectotypified Pseuderanthemum maculatum (G.Lodd.) I.M.Turner (
Pseuderanthemum melanesicum Gâteblé, Ramon & Butaud is most similar to some cultigens of P. carruthersii but differs from them by its carnose leaf texture vs. chartaceous, by its pedicels and sepals with glandular hairs vs. eglandular hairs, by its glabrous petals and tube vs. hairy petals and tube and by its short and enlarged corolla tube vs. longer cylindrical corolla tube.
NEW CALEDONIA. Province des Iles Loyauté: Lifou, plant cultivated at the Agricultural Research Station Saint Louis at Mont-Dore, 4 December 2018, G. Gâteblé 1072 (holotype P; isotypes NOU [NOU089981, NOU090339]).
Fruticulose shrubs up to 1.5 m tall, generally decumbent to somehow erect, somewhat carnose. Branches round (living material) to angulate (dry material) in cross section, beige to brown on older stems, pale green on young stems; prominent leaf and bundles scars; lenticels few, glabrous. Leaves simple, opposite-decussate, usually ovate to broadly elliptic, rarely obovate; blade (7–) 8–11 (–12) × (2.5–) 5–6 (–6.5) cm, vernicose, carnose, glabrous on both surfaces; apexes obtuse to rounded, sometimes slightly retuse or acuminate, bases cuneate to attenuate, margins entire; midveins slightly impressed adaxially, prominent abaxially toward the base, glabrous; secondaries of 4–6 opposite or alternate veins, more or less brochidodromous; tertiaries in a loose reticulum; petioles (0.5–) 1–1.5 (–2.5) cm long. Inflorescences terminal, a raceme or panicle, 1–12 cm long; rachises round to quadrangulate in cross section, mostly glabrous but with some glandular hairs in its most apical part; peduncles 1–5 cm long usually glabrescent but sometimes with some glandular hairs; bracts and bracteoles lanceolate 1–4 mm × 0.5–1.5 mm, glabrescent to piloglandulose. Flowers bilaterally symmetrical; pedicels 3–11 mm long, piloglandulose. Sepals 4 or 5, lanceolate, 3.5–4 × 1 mm, piloglandulose on the outer surface, glabrescent inside. Corollas ampliate to slightly ventricose, white with purple center, aestivation imbricate in bud; tubes ca. 1–1.3 cm long, glabrous, enlarged distally to 3–5 mm diameter before the throat, 4–5 lobed, consistently three in the lower half, and one or two in the upper half; lobes elliptic, 5–8 × 4–7 mm, the lower one being the larger, glabrous. Stamens 2, slightly exserted, inserted in the tube orifice on to the upper lobe(s), filaments 4–4.5 mm long, glabrous, anthers ca. 1.8 × 0.8 mm; staminodes 2, ca. 1 mm long. Ovaries conical, 4.5 × 2 mm, glabrous; styles slightly exserted, ca. 15 mm long, glabrous; stigmas bilobed, lobes ca. 0.5 × 0.15 mm. Fruits stipitate dehiscent capsules, clavate, 1.5–3 × 0.6–0.8 cm, sometimes crowned with the remnant style; seed (4–?) per capsule, ovate, 3–4 mm × 2–3 mm.
In New Caledonia and Vanuatu, P. melanesicum is found in coastal thickets on limestone substrate, either coastal reef, cliffs or back of the beaches, with species of Bikkia Reinw. ex Blume, Dendrolobium (Wight & Arn.) Benth., Eugenia P.Micheli ex L., Heliotropium Tourn. ex L., Hibiscus L., Myoporum Banks & Sol. ex G.Forst., Nicotiana L., Pemphis J.R.Forst. & G.Forst., Sarcolobus R.Br. and Xylosma G.Forst. at 2–60 m elevation in the Loyalty Islands. In New Caledonia, it is only known from Lifou and Maré in the Loyalty Islands and it is known from Efaté and Malakula in Vanuatu (Fig.
Drawings of Pseuderanthemum melanesicum Gâteblé, Ramon & Butaud, sp. nov. and P. carruthersii A–G Pseuderanthemum melanesicum H–I Pseuderanthemum carruthersii A, D Structure of the inflorescence B Flower C Flower bud E Open corolla with the lower corolla lobe removed to show the arrangement of internal structures F Open mature and immature capsules G Glandular hairs on a flower bract H Eglandular hairs on the outer surface of the corolla tube I Part of inflorescence showing the long narrow tube of a flower. Voucher specimens: A–D Gâteblé 1072 E, G Gâteblé 722 F Ramon 220 H–I Gâteblé 720. Drawings by Laurence Ramon.
The new species is named after the Melanesian archipelagos of New Caledonia and Vanuatu.
With its carnose and shiny leaves (especially seen on fresh material), its short and broaden corolla tube and its many glandular hairs on pedicels and sepals, P. melanesicum is easily separated from the cultivated, widespread and variable taxon, P. carruthersii. In addition, in both countries the new species has been collected in fruit while there is, to our knowledge, no fruiting specimen of P. carruthersii in the region. The well-known south-western Pacific botanical specialist Peter Shaw Green (1920–2009) also thought it was a putative new species as he wrote “Pseuderanthemum sp.? ined” on several herbarium sheets (e.g., Hallé 6331 and Gillison 3539).
Color figures of P. melanesicum have already been published twice under misapplied names of other species inhabiting Loyalty Islands and Vanuatu, once as P. repandum subsp. loyaltyensis (Guillaumin) Heine or «Waditcha» in
The cultivated plant from which the type specimen was prepared was originally collected by J.-F. Butaud on Lifou, north of Wé to Luecila, (2 m elevation, 20°53'34.56"S, 167°16'18.56"E) on 19 April 2014.
Field pictures of Pseuderanthemum melanesicum Gâteblé, Ramon & Butaud, sp. nov. and P. carruthersii A–D. Pseuderanthemum melanesicum E–F Pseuderanthemum melanesicum and P. carruthersii A Overview of a single shrub hanging from a coastal limestone cliff on Maré island B Flowering branch on Efaté island C Flower D Infructescence and ecology on Lifou island E Cultivated plants of P. carruthersii (left) and P. melanesicum (right) F Leaves and inflorescences of P. melanesicum (left) and two cultigens of P. carruthersii (center and right). Photographs by G. Gâteblé (A, C, E–F), L. Ramon (B) and J.-F. Butaud (D); Voucher specimens: A Gâteblé et al. 1024, B Ramon 220, C Gâteblé 722, F Gâteblé 722, 721, 720.
In New Caledonia, the species is very uncommon and was collected only recently from the east coasts of Lifou and Maré islands. Recently 15–20 shrubs were seen on Lifou and two on Maré but B. Suprin (pers. comm., 2015) states he has seen it in a few places on Maré and Lifou. On Maré, the species is threatened by feral goats that seem to graze young stems and that contribute to habitat degradation. On Lifou, in its only currently known location, the species is not clearly threatened; the only threats could come from agriculture as nearby areas are cultivated. The distribution of P. melanesicum in New Caledonia is similar to that of Cyrtandra mareensis Däniker but much rarer for the number of individuals. Its area of occupancy is 8 km2 while its extent of occurrence is less than 500 km2. It is considered severely fragmented as each subpopulation could go extinct with a very reduced probability of natural recolonization from the other subpopulation. A continuing decline has been observed and/or estimated for its quality of habitat and number of mature individuals. Based on the IUCN Red List Categories and Criteria (
NEW CALEDONIA. Province des Îles Loyauté: Lifou, Luecila, 2 m, 20°53'34.56"S, 167°16'18.56"E, 15 April 2015, J.-F. Butaud 3427 (NOU [NOU090338]); plant cultivated at the Agricultural Research Station Saint Louis at Mont-Dore, 13 May 2015, G. Gâteblé 679 (NOU [NOU089984]); ibid. loc., 7 December 2015, G. Gâteblé 722 (NOU [NOU089982, NOU089983]); ibid. loc. 29 December 2015, G. Gâteblé 740 (NOU [NOU089985, NOU090341]); ibid. loc. 19 February 2019, G. Gâteblé 1073 (NOU [NOU090340]). Maré: Sentier littoral entre Eni et Shabadran, 60 m, 21°39'25.57"S, 168°0'22.45"E, 2 April 2018, G. Gâteblé, Drouin J, Jewine A. & Wamejongo W 1024 (MPU, NOU |NOU089986], P, K, LOY). VANUATU. Efaté, Eton, plage privée (avant le blue hole), 0 m, 17°45'0.55"S, 168°33'55.46"E, 5 August 2015, L. Ramon 220 (NY [NY03487104], P [P02434405], PVNH). Malekula, Tisbel, 29 September 1971, N. Hallé 6331 (NOU [NOU077567], P [P04385831]); ibid. loc., 28 September 1971, A.N. Gillison 3539 (P [P04385834]).
We are grateful to Jacqueline Tinel and the team at the NOU herbarium (IRD, Nouméa) for mounting, distributing and computerizing the specimens. Special thanks to Jérôme Munzinger who has checked the specimens at P for us. We also thank the authorities of Loyalty Islands Province (DDRA) and Vanuatu for providing collecting permits. Warm regards to Anne Marshall from the Kew Library for sending the W. Bull catalogue of 1874. Gildas Gâteblé is most thankful to Julien Drouin and Jacques Wamejongo for their enthusiastic help in the field and Giliane Karnadi-Abdelkader and Jacqueline Ounémoa, propagation and cultivation of the new species in the Saint-Louis research facilities and to L.A. McDade and B. Suprin for their personal communications. Armelle Tardivel mounted Figure