Research Article |
Corresponding author: Jean-François Butaud ( jfbutaud@hotmail.com ) Academic editor: Daniel Nickrent
© 2015 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:
Butaud J-F (2015) Reinstatement of the Loyalty Islands Sandalwood, Santalum austrocaledonicum var. glabrum (Santalaceae), in New Caledonia. PhytoKeys 56: 111-126. https://doi.org/10.3897/phytokeys.56.5924
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Sandalwoods encompass 19 species restricted to southeast Asia and the Pacific. The species Santalum austrocaledonicum Vieill. (Santalaceae) is endemic to New Caledonia (Grande-Terre, Isle of Pines, Loyalty Islands) and Vanuatu, where several varieties are recognized. The Loyalty Islands sandalwood variety is here reinstated as Santalum austrocaledonicum var. glabrum Hürl. emend. Butaud & P.Firmenich, mut. char. It was previously considered a synonym of the type variety; however, new morphological and genetic studies confirmed its distinctiveness. The key for New Caledonian varieties of Santalum austrocaledonicum has been updated and a short description of its essential oil composition and organoleptic quality is given.
Santalum austrocaledonicum , Santalaceae , Loyalty Islands, New Caledonia, essential oil
Sandalwoods are shrubs or small trees well known for the essential oil extracted from their fragrant heartwood and used in perfumery. They belong to the genus Santalum (Santalaceae) comprising 19 species restricted to southeast Asia and the Pacific (
Santalum austrocaledonicum Vieill. is the only native sandalwood in New Caledonia and Vanuatu (
The most recent taxonomical work on S. austrocaledonicum was carried out by
S. austrocaledonicum var. austrocaledonicum from Grande-Terre (main island of New Caledonia), Isle of Pines, Loyalty Islands and Vanuatu;
S. austrocaledonicum var. pilosulum N.Hallé in the vicinity of Nouméa on the southwest coast of Grande-Terre;
S. austrocaledonicum var. minutum N.Hallé from the northwest coast of Grande-Terre.
Since that revision, several studies have shown the great morphological variations of var. austrocaledonicum in New Caledonia and Vanuatu which are linked to geographical distribution (
Loyalty Islands: large seeds (L = 8–11 mm, D = 7–10 mm), short and wide juvenile leaves (L = 30–52 mm, W = 8–15 mm);
Isle of Pines: medium-sized seeds (L = 8–10 mm, D = 6–9 mm), long and narrow juvenile leaves (L = 25–76 mm, W = 2–10 mm);
Grande-Terre: small seeds (L = 6–9 mm, D = 5–7 mm), long and very narrow juvenile leaves (L = 52–70 mm, W = 2–4 mm).
No comprehensive study of the variation of these characters is available in Vanuatu due to lack of herbarium specimens from most of sandalwood populations there.
For this reason,
More recently, molecular studies of New Caledonian sandalwood showed strong genetic differentiation between islands and led to the recognition of two evolutionarily significant units, i.e. Grande-Terre and Isle of Pines for the first, and Loyalty Islands for the second (
The New Caledonian sandalwood is subject to exploitation through harvesting and is grown in plantations to satisfy the increasing international demand of sandalwood essential oil. However, its taxonomy appears to be in need of revision to more precisely describe the variability of this New Caledonian biodiversity hotspot species (
A first step of this revision is presented here, with the recognition of an endemic sandalwood variety from the Loyalty Islands based on morphological and molecular studies as well as examination of living plants and herbarium specimens.
The New Caledonian sandalwood, Santalum austrocaledonicum, was described by
In 1964, Hürlimann described a new variety based on a sample collected on the island of Maré in the Loyalty Islands (
In 1988, the revision of the New Caledonian Santalum by Hallé recognized the three varieties mentioned in the introduction. Hallé reduced var. glabrum of Hürlimann to synonymy under the type (autonym) variety, considering it superfluous due to confusion by Hürlimann on what was really the type of the species. Indeed, the latter described var. glabrum in comparison with what is now recognized as var. pilosulum, this one differing morphologically from var. austrocaledonicum. The true var. austrocaledonicum and var. glabrum are in fact identical relative to the morphological differences pointed out by Hürlimann in his diagnosis.
As the native Loyalty Islands sandalwoods are quite homogeneous, only one variety is to be recognized for the entire Loyalty archipelago, which is the one of Hürlimann. Thus, to reinstate the varietal name glabrum for the endemic Loyalty sandalwood, its description must be amended to distinguish it from the true type specimen.
S. austrocaledonicum var. glabrum Hürl., Mém. Mus. Hist. Nat., ser. B, Bot. 15(1): 15 (1964).
New Caledonia, Loyalty Islands, Maré, près de Rawa, arbre, 8 m, en fleurs et en fruits, forêt mésophile, 17 July 1951, M.G. Baumann-Bodenheim 14762 (holotype: P scan!; isotype: Z scan!).
Santalum austrocaledonicum var. glabrum is most similar to var. austrocaledonicum in its glabrous inflorescence and leaves wider than 1.5 cm, which differentiates them from the other New Caledonian S. austrocaledonicum varieties. Santalum austrocaledonicum var. glabrum differs from S. austrocaledonicum var. austrocaledonicum by the seed size, which is more than 7.5 mm wide for the former and less than 7.5 mm for the latter.
Shrub to small tree 2–10 m tall, trunk up to 30 cm dbh; bark rough, grey to reddish-brown, longitudinally fissured; heartwood fragrant, yellowish to brownish. Leaves glabrous; petiole canaliculate, 7–13 mm long; blades of the mature leaves 3.5–6.0 (–6.6) × (1.6–) 2.0–3.5 (–4.1) cm, usually elliptic or rarely obovate, apex obtuse to acute or apiculate, base acute, secondary veins mostly 7–9 pairs. Inflorescences glabrous, in axillary or terminal panicles, usually trichotomous and several times branched, with 10–40 flowers; peduncles 10–38 mm long. Flowers bisexual with outer surface of petal greenish and glabrous; pedicels 1.5–2 mm long. Petals 4, narrowly triangular, 2.5–3.0 × 1.5–2.0 mm, inner surface white when opening turning brownish later; petal internal margin glabrous. Stamens 4, surrounded by long hairs at the base; the outer ones reaching the anther apex, the inner ones reflexed in the cup-shaped disk; anthers 1.5–2.7 × 0.8–1.0 mm. Disk concave, more than 2 mm deep; disk lobes fleshy and erected between petals, 1.3–1.4 × 0.8–0.9 mm. Ovary unilocular, conic, acute, 1.1–1.7 × 0.6 mm; style free, 4 mm long; stigma 3 or 4 lobed. Fruit a globose fleshy drupe, 15–21 × 12–15 mm when fresh, topped by the petal scars 3–5 mm diameter, green turning red to deep purple and black at maturity. Seed globose, with a hard endocarp (8.5–) 9.0–11.5 × 7.5–10.0 (–10.5) mm.
Flowering and fruiting probably occurring throughout the year but with some peaks; herbarium samples provide the following data: flowers from December to August, fruits from January to August.
This variety is restricted to the calcareous soils of uplifted atolls between 5 and 80 m elevation and is closely linked with traditional agriculture which consists of shifting cultivation. Regeneration by seeds occurs mainly in the open cultivated areas and young fallow lands. Loyalty sandalwood is therefore characteristic of fallows, shrublands and secondary forests, and rarely occurs in mature forests. It is also commonly found along roads and close to villages in open areas where it is generally protected and managed by inhabitants. The surrounding vegetation is often composed of trees and shrubs, such as Acacia spirorbis Labill., Acalypha spp., Acronychia laevis J.R.Forst. & G.Forst., Dodonaea viscosa (L.) Jacq., Elattostachys apetala (Labill.) Radlk., Glochidion billardierei Baill., Melochia odorata L.f., Morinda citrifolia L., Pandanus macrocarpus (Brongn.) Solms, Podonephelium homei (Seem.) Radlk., Polyscias bracteata subsp. bracteata., Psidium guajava L., and Schinus terebenthifolius Raddi. Loyalty sandalwood is a hemiparasitic tree like all Santalum species; its pollination is insect-mediated whereas its fleshy fruits are dispersed mainly by doves and pigeons (
Using the categories and criteria of
The common names recorded for S. austrocaledonicum var. glabrum are “tapakae” (pers. obs. 2014) or “tapakai” (
Santalum austrocaledonicum var. glabrum is the sole native sandalwood in the Loyalty Islands. Nevertheless, two other varieties have been introduced for plantation purposes, mainly in Maré and Lifou: var. pilosulum from Ouen Toro in Nouméa, and var. austrocaledonicum from Isle of Pines. These plantations can be considered a risk for the Loyalty variety because of hybridization and subsequent introgression. Plantations with exotic varieties should be discouraged to preserve the Loyalty sandalwood’s morphological, genetic, sylvicultural and chemical specificities (
The taxonomy of S. austrocaledonicum still needs to be further investigated. Indeed, the study of herbarium samples of var. austrocaledonicum and previous molecular and morphometric studies (
(adapted from
1 | Inflorescence peduncles, rachis segments and outer surface of petals sparsely to densely hairy | var. pilosulum |
– | Inflorescence peduncles, rachis segments, outer surface of petals and petal internal margins glabrous | 2 |
2 | Leaf blade usually less than 3.5 × 1.5 cm; petiole less than 7 mm; blade adaxial surface glaucous and bluish in color; interstaminal disk lobes very narrow (W/L = 1/3–1/4) | var. minutum |
– | Leaf blade usually more than 3.5 × 1.5 cm; petiole more than 7 mm; blade adaxial surface not glaucous and bluish in color; interstaminal disk lobes wide (W/L = 1/2) | 3 |
3 | Seed usually more than 9 × 7.5 mm; globose (L/D < 1.2) | var. glabrum |
– | Seed usually less than 9.5 × 7.5 mm; ovoid (L/D > 1.2) | var. austrocaledonicum |
Essential oil of Santalum austrocaledonicum was previously assessed for its composition and organoleptic properties, and was considered as a possible substitute for Indian sandalwood oil (Santalum album) but also as a promising new raw material for the fragrance industry (
To investigate the quality of Loyalty Islands sandalwood essential oil (var. glabrum), two samples were analyzed for their main sesquiterpenoids but also for their organoleptic properties:
Loyalty Oil 1 (EI1) obtained in 2015 from Distillerie de Boulouparis (New Caledonia) with Ouvéa sandalwood,
Loyalty Oil 2 (EI2) obtained in 2002 from Michel Point and processed by Koop Cuada distillery with Maré and Lifou sandalwoods.
The gas-chromatography was performed on an apolar column (HP-1, 10 m x 0.1 mm, film 0.1m, 50° (1’) to 280° (2’) at 50°/min., vector gas: hydrogen). Its results are given in Table
The organoleptic evaluation showed that the Loyalty essential oil is lighter and less milky than the Indian sandalwood; the former has also a character less woody but more animal and masculine (P.-A. Blanc and S.A. Firmenich, pers. comm. 2015).
Main constituents of Loyalty Islands sandalwood (var. glabrum) essential oil compared to ISO standards for S. album oil.
Essential oil | (Z)-α-santalol (%) | (Z)-β-santalol (%) | (E)-lanceol (%) |
---|---|---|---|
ISO Standard 3518 : 2002 (S. album) | 41 to 55 | 16 to 24 | - |
New Caledonia |
38.2 | 18.2 | 9.1 |
Loyalty Oil 1 | 44.3 | 19.4 | 14.1 |
Loyalty Oil 2 | 47.4 | 21.3 | 8.5 |
These findings are in accordance with
I am grateful to the Province des Iles Loyauté (PIL) which has initiated and supported recent investigations on the Loyalty Islands flora, to the Firmenich Charitable Foundation for supporting taxonomical studies, and to the Herbier du Centre IRD de Nouméa (
I thank Gildas Gâteblé (Institut Agronomique néo-Calédonien) for helpful discussions on Loyalty Islands Santalum, and, together with David Lorence (National Tropical Botanical Garden, Hawai’i), Art Whistler, and Jacques Florence (IRD), for their important comments and corrections of previous drafts of this paper. I appreciate review comments by Daniel Nickrent and an unknown reviewer.
I am indebt to Christian Vial and Pierre-Alain Blanc (Firmenich S.A.) for, respectively, gas-chromatography analysis and organoleptic analysis of S. austrocaledonicum var. glabrum essential oils, and to Annette Olsson (Conservation International) for English wording review. I am also grateful to George Kakue, Luen Iopue, Meri Thupalua (PIL) and Jean-Christophe Lefeuvre (Conservation International) for their support and interest in establishing a Flora of Loyalty Islands, and to Selma Haouet for providing the map background.
Specimens examined
Santalum austrocaledonicum var. glabrum Hürl.: New Caledonia, Loyalty Islands.
Ouvéa. Lékine, 15 May 1976, D. Bourret 815 (
Lifou. July 1869, B. Balansa 1692b (P scan); 1928, C. Bergeret 106 (P scan); Mutschaweng, 30 m, lisière de forêt, 18 February 1974, H.S. MacKee 28169 (P scan, Z n.v.); Natchaom, 5 June 1987, H.S. MacKee 43577 leg. Wapae (P scan); Natchaom, 5 June 1987, H.S. MacKee 43578 leg. Wapae (P scan); Natchaom, 5 June 1987, H.S. MacKee 43579 leg. Wapae (P scan); Ouanaham, 3 August 1987, H.S. MacKee 43638 leg. Case (
Maré. Medu, dans les fourrés, 22 December 1925, A.U. Däniker 2546a (P scan, Z n.v.); E.I. Franc 1286 (P scan); La Roche, fourré secondaire, 24 April 1987, H.S. MacKee 43602 leg. Cornaille (
Santalum austrocaledonicum var. austrocaledonicum:
New Caledonia, Grande-Terre. Arama, collines près de la mer, 1855-60, E. Vieillard 1090 (holotype: P scan; isotypes: P [2] scan, K p.p. scan); Arama, collines près de la mer, 1855-60, E. Vieillard 1090bis (P scan; K p.p. scan); Vavouto, 26 September 2007, J. Munzinger 4518 (
New Caledonia, Isle of Pines. 1852, Home s.n. (BM scan); 1853, MacGillivray 818b (K scan); ); Kuto, 1 February 1980, H.S. MacKee 37852 leg. Douheret (
Santalum austrocaledonicum var. pilosulum N.Hallé: New Caledonia, Grande-Terre. Nouméa, Ouen Toro, 50 m, forêt côtière sur pente caillouteuse schisteuse 29 December 1971, H.S. MacKee 24766 (holotype: P scan); Mont Dore, Ilot Pêcheur, 27 January 2015, G. Gâteblé 708 (
Santalum austrocaledonicum var. minutum N.Hallé: New Caledonia, Grande-Terre. Montagne de Poum, pic 272, versant Est, 50 m, arbuste 3m, 25 March 1982, J.M. Veillon 4852 (holotype: P n.v.; isotype