Bocquillonia corneri Bruy, Barrabé & Munzinger, 2018

Bruy, David, Barrabé, Laure & Munzinger, Jérôme, 2018, Novitates neocaledonicae VII: A new monocaulous species of Bocquillonia (Euphorbiaceae) from New Caledonia, Phytotaxa 360 (1), pp. 61-68 : 63-65

Bocquillonia corneri Bruy, Barrabé & Munzinger sp. nov. ( Figs. 2 , 3 )

Type: — NEW CALEDONIA. Province Nord. Commune de Ouégoa: Base du col d’Amoss, 105 m, 20°19’2.4”S, 164°25’22.8”E, 11 August 2017 (fl.), Bruy, Barrabé & Hattermann 923 [♀] (Holotype P 01156371!, Isotypes NOU 088193!, MPU 310860!, K!, MO!, BRI!).

Diagnosis:—Vegetatively, Bocquillonia corneri resembles B. castaneifolia Guillaumin in its monocaulous architecture, its oblanceolate to obovate blade shape and in having very short petioles. Bocquillonia corneri differs most notably from the latter species by the dimensions of the stem (up to 8 cm DBH and 8 m height, vs. 3 cm and 2 m), petiole length (> 9.4 mm, vs. <5 mm) and blade length (> 25 cm long, vs. <24 cm) and in having caducous stipules (vs. persistent) and stigmas applied against the ovary in female flowers (vs. erect).

Based on reproductive organs, Bocquillonia corneri resembles B. sessiliflora Baillon (1862: 226) , which has also condensed inflorescences and in which the stigmas are oval and applied against the ovary. Bocquillonia corneri differs most notably from the latter species by the strictly monocaulous architecture (vs. well reiterated treelet), the narrowly oblanceolate leaf blade (vs. ovate to oblong), the lack of an upper pulvinus on the petiole (vs. present) and the fushia calyx in vivo (vs. green).

Monocaulous treelet to monocaulous tree, 1.50 m to 8.00 m tall, sometimes with a few reiterations.

Stem glabrous, light grey to white, with brown longitudinal scars; young stems bearing alternatively cataphylls and pseudoverticillate assimilative leaves bundled at the proximal part of the stem.

Stipules caducous, subulate, 3–7 mm long, 0.5–1.2 mm wide, dark brown in sicco, glabrescent. Cataphyll: caducous, narrowly lanceolate, navicular, pectinate, 6–11 (–15) mm long, 0.8–2.1 mm wide, densely strigose with silvery trichomes in sicco. Assimilative leaf: blades narrowly oblanceolate, (24.6–) 36.1–72.5 × 6–16.5 cm, dark purple when young, then pinkish and green when mature, chartaceous to subcoriaceous, adaxial surface glabrous, abaxial surface nearly glabrous; base cuneate to rounded, sometimes asymmetrical; apex acuminate to acute, rarely rounded; margin dentate and minutely revolute; leaf teeth (13–) 21–27 on each side, white on young leaves, black on mature leaves; sunken laminar glands (6–) 13–34 (–49) on each side of the midrib, circular to elliptic, (0.3–) 0.5–1.3 (–1.5) mm in diameter, black in sicco, generally close to the midrib. Venation craspedodromous; midrib not or barely raised adaxially, prominent abaxially, pink to purple when young, green when mature, glabrous adaxially, sparsely and obscurely appressed-puberulent abaxially; secondary veins (16–) 24–30 on each side of the midrib below the acumen, raised adaxially, prominent abaxially, spaced from 8–38 mm, angle with midrib 48–92 °, glabrous; tertiary venation scalariform, not or barely raised on both surfaces, glabrous; quaternary venation obscure adaxially, minutely raised abaxially, glabrous. Petioles without an upper pulvinus, flat adaxially, subtriangular in cross section, 9.4–34.4 mm long, 3.3–7.1 mm in diameter, pink to purple when young, green when mature, striate in sicco, sparsely and obscurely appressed-puberulent to glabrous.

Plants dioecious, sometimes monoecious. Inflorescences reduced to cauliflorous glomerules sometimes axillary to oldest leaves, borne on short shoots; staminate inflorescences (3.5–) 4.4–7.8 mm long, 4.5–14.5 mm in diameter; bracts ovate, with an acuminate to rounded apex, reducing in size from outside to inside of the inflorescence, fushia, sparsely pubescent and ciliate. Staminate flowers glabrous, pedicel ca. 1.5–3.5 mm long, ca. 0.4–1 mm wide, white pinkish; calyx (2-) 3-lobed, fushia, lobes ovate, 0.8–3.1 mm long, 1.5–2.6 (–3) mm wide, with an obtuse to acute apex, with a turbinate tube 2.3–3.8 mm long, 1.8–2.9 mm wide; stamens 2–4, connate at the base, fushia, glabrous, anthers 0.8–1.9 × 1.0–2.0 mm, filaments 1.8–3.6 mm long above the connate section, 0.25–0.60 mm wide, pistillode lacking. Pistillate inflorescences 6.5–13.5 mm long, (7–) 9.9–16.7 (–18.5) mm in diameter, bracts ovate, 1.8–5.6 × 1.7–5.1 mm, with a rounded to acute apex, fushia, ciliate and pubescent, glands present. Pistillate flowers fushia, sessile; sepals 4–5, ovate, 2.2–5.6 mm long, 1.8–4.4 mm wide, with an acuminate apex, ciliate, pubescent to sparsely pubescent; stigmas (2–) 3 (–4), oval, slightly domed, papillate, applied against the ovary; ovary spherical, 2.7–4.6 mm in diameter, densely hirsute. Fruit 3-lobed, ca. 9 mm long, 9–11 mm in diameter, exocarp rugulose, ochre in sicco, sparsely strigose with silvery trichomes; placental column 5.5 mm long; seeds 6–7 × 4.5–5.5 mm, covered with low, blister-like swellings, dark grey in sicco.

Phenology:—Flowers of Bocquillonia corneri have been observed in March, August and November, and mature fruits have been collected in April and August.

Distribution and Ecology:—This new species is only known from the Indanou creek, at the base of Col d’Amoss in the north-eastern part of Grande Terre, in Province Nord, near Ouégoa village ( Fig. 4 ), where it occurs in thalweg (gully) forest on volcano-sedimentary substrate, more specifically on micaschists, at around 60–150 meters elevation. Only 56 adult individuals are known but intensive field prospection in the area could potentially locate other individuals.

Etymology:—The plant is named in honour of E.J.H. Corner who provided interesting insights about monocaulous plants and whose theories inspired generations of botanists. In addition, the architecture of this plant conforms perfectly to the Corner’s architectural model ( Hallé et al. 1978).

Species recognition:— Bocquillonia corneri is easily recognizable in the field because it is the only species of the genus that is a very few times reiterated monocaulous tree. It is also the only species to combine condensed inflorescences, pistillate flowers with a fuchsia calyx and oval stigmas applied against the ovary.

Conservation status:— Bocquillonia corneri is only known from a single population, critically threatened by fire,

human activity and invasive species, in particular the deer Rusa timorensis de Blainville (1822: 267) . The population corresponds to one unique location sensu IUCN since all individuals could be affected by a single threatening event.

Only 56 mature individuals are known, with approximately 25 female individuals. Even though individuals not seen by the authors may be present in the region, it is very probable that the population is smaller than 250 mature individuals.

The EOO calculated is 0.092 km ² and the AOO is 4 km ². We assign consequently a preliminary conservation status of

Critically Endangered to B. corneri (CR) B1 ab(iii,v)+2ab(iii,v) using the IUCN Red List criteria ( IUCN 2012).

Additional specimens examined (Paratypes): — NEW CALEDONIA. Ouégoa. Route Koumac–Ouégoa, peu avant le Col d’Amoss, 28 November 2008 (fl.), Barrabé & Létocart 788 [♂] ( NOU033871 ) ; Ouégoa : Base du col d’Amoss, 100 m, 20°19’40.6”S, 164°25’34”E, 11 August 2017 (fl.), Bruy, Barrabé & Hattermann 921 [♂]

(BRI, K, MO, MPU310861, NOU088196, P01156372); Païta : Chez D. et I. Létocart, 1 June 2017 (fl.) [Cultivated plant], Bruy, Barrabé & Létocart 807 [♂] ( NOU088195 ) ; Nouméa : Val Plaisance, Chez J. M. Veillon, 16 June 2017 (fl.) [Cultivated plant], Bruy, Barrabé & Veillon 879 [♀] ( NOU088194 ) ; Ouégoa : Indanou (Amoss), 41 m, 20°19’18.947”S, 164°25’23.058”E, 10 March 2016 (bd.), Fleurot 224 [♂] ( NOU085638 ) ; Ouégoa : Indanou (Amoss), 41 m, 20°19’19.722”S, 164°25’23.380”E, 27 April 2018 (fr.), Fleurot 433 [♀] ( NOU088719 ) ; Ouégoa : Col d’Amoss, 200–300 m, 19 October 1956 (fr.), MacKee 5479 [♀] ( L0449021 , P00160238 ) ; Ouégoa : Bas du col d’Amoss, côté Ouégoa, 10–20 m, 27 August 2006 (fr.), Munzinger 3544 (Leg. D. et I. Létocart) [♀] ( NOU013877 ) .

Figures

FIGURE 2. Pictures of Bocquillonia corneri. A—Early mature individual in its natural environment; B—Bark and slash with old staminate inflorescences; C—Apex and flushing young leaves; D—Detail of nervation and glands of the abaxial surface; E—Pistillate inflorescences; F—Staminate inflorescences. Photographers: Barrabé L. & Bruy D.

FIGURE 3. Drawing of Bocquillonia corneri. A—Mature leaf; B—Detail of venation; C—Stem apex with stipules; D—Male flower; E—Female flower; F—Fruit; G—Seed in ventral (left) and dorsal face (right). Illustrator: Ramon L.

FIGURE 4. Distribution map of Bocquillonia corneri in the North Province and detail of the distribution of known individuals along Indanou creek. Numbers near the yellow dots represent the number of individuals.