Acropogon mesophilus Munzinger & Gâteblé, 2017

Munzinger, Jérôme & Gâteblé, Gildas, 2017, Novitates neocaledonicae VI: Acropogon mesophilus (Malvaceae, Sterculioideae), a rare and threatened new species from the mesic forest of New Caledonia, Phytotaxa 307 (3), pp. 183-190 : 185-188

Acropogon mesophilus Munzinger & Gâteblé , spec. nov. ( Figs. 1 , 2 )

Type:— NEW CALEDONIA. Province Sud: Boulouparis, Camp Brun, le long de la Diahot, 130 m, 21°49’29.85”S, 165°54’50.71”E, 30 September 2015, Gâteblé 711 (holotype P-01069417!; isotypes G!, K!, MEL!, MPU-028533!, MO!, NOU-081994!, NOU-081995!, P-01069418!) .

Diagnosis:— Acropogon mesophilus Munzinger & Gâteblé differs from A. bullatus and A. veillonii by its flat, ovate leaf blade, with base truncate to rounded, three main palmate veins and many evident domatia, and by its yellow sepals with 2–4 grayish-purple stripes per calyx lobe.

Monoecious tree to 15 m tall, well branched with usually a main trunk of up to 45 cm in dbh; bark gray, with evident petiole and scales scars on terminal branches. Leaves usually clustered at the apex of branches, these 3.5–8 mm in diameter; petioles light green to yellow–orange (dark green to blackish in herb.), strongly discolorous to the branch, glabrous, (30–)50–90(–170) mm long, (1–)2(–3) mm in diam., usually longer and wider on vegetative shoots, and shorter and narrower on fertile ones, elliptical in cross section (on fresh material), enlarged (3–5 mm) proximally and distally, these pulvini generally pruinose on fresh material; blades simple, unlobed to slightly (rarely strongly as in Gâteblé et al. 685) trilobed, usually widely ovate, flat (i.e., not bullate), papyraceous to coriaceous, (81–)100–170(– 230) mm in length, (52–)70–150(–220) mm in width (usually larger on sterile shoots, and smaller on fertile ones), base truncate to rounded, apex broadly acute to rounded, slightly discolorous, glabrous on both surfaces; generally with 3 strong primary (+ 2 smaller ones) palmate veins, primary and secondary veins prominent on both surfaces, reticulum visible abaxially, 3–5 pairs of secondary veins; tertiary veins inconspicuous; round or elliptic hole-like domatia visible on the lower surface of the leaf, generally present in the angles between the primary and secondary veins, sometimes also in the angles between secondary and tertiary veins. Inflorescence axillary within, above or just below the terminal bouquet of leaves and up to 6.5 cm long, axes grayish-purple [group 183 A –D of RHS 2001] to green covered with grayish–yellow tomentum, bracts covered with gray tomentum adaxially (sometimes glabrous and grayish-purple), always covered with gray tomentum abaxially. Pedicels (1–)4(–5) mm long, 0.5 mm wide at widest part, covered with grayish–yellow tomentum, articulated 0.1–0.5 mm below the calyx. Flowers ♀ appears less numerous than ♂, and seems randomly distributed in the inflorescence.

Flowers ♂ and ♀ of the same size and perianth. Calyx 8–12 mm long, 7 mm in diameter, yellow [group 10 C –D

of RHS 2001] with 2–4 grayish-purple [group 187 A –D of RHS 2001] stripes per calyx lobe, fused basally ca. 5 mm, lobes (4–)5(–6), 4–5 mm long, triangular-fimbriated. Flowers ♂: androecium (3–)4(–5) mm long; androphore 3–4 mm long; stamens 5–7, 1–1.5 mm long, inserted at apex of androphore. Flowers ♀: Staminodes 5–7, sessile, ca. 0.5mm

long inserted at base of carpels. Gynoecium sessile 4–5 mm long; carpels 3–4, 3–4 mm long; styles ca. 1 mm long,

covered with dense tomentum; stigmas ovoid.

Infructescence 5–15 cm long, robust, on a peduncle 2–8 cm in length. Fruit 1–3 follicles with pedicels of 0.5–1

cm long and 0.3–0.4 cm in diameter at maturity, green prior to maturity and turning greenish–yellow–light purple at maturity, covered by sparse stellate hairs, each follicle ellipsoid to ovoid, 3.5–6 × (1.5–) 2.5–3.5 cm, with a woody pericarp 0.3–0.4 cm in dry material (up to 6 mm in alcohol) in thickness, apex rounded, sometimes with a stipe up to 1

cm long and 0.5–0.7 cm in diameter. Seeds ellipsoid, light brown or black, 4–6(–8) per locule, 1.2–1.5 cm long × 7–10

mm in diameter.

Distribution and Ecology:—The tree is only known from the southwestern part of the Grande-Terre, around La

Foa and Boulouparis ( Fig. 3 ), where it grows in mesic forest along rivers.

Phenology and notes regarding biology of the species:—Flowering in A. mesophilus occurs during the dry season (September to December). Flowering begins in September, and at this first stage, all open flowers are male

[Gâteblé 711]. By November, flowering is at its peak, and there are male and female flowers and even the first young fruits [Gâteblé 719]. Flowering ceases in late December, as fruits are increasing in size. Mature fruits are produced mainly between May and July [Gâteblé et al. 685 & Gâteblé 686], i.e., during the cool wet season, when conditions should be ideal for the germination of these, potentially non-dormant, recalcitrant seeds (G. Lannuzel, pers. comm., from an experiment on A. macrocarpus Morat & Chalopin (2003: 198)) . An adult of Chrysocoris aff. sexmaculatus ( Leach1815: 36) ( Scutelleridae ) was observed foraging deeply in the male flowers and bearing pollen on its front legs and antennas. A caterpillar, probably belonging to the common endemic Euproctis dimorphissima ( Holloway 1979: 363) , was also observed consuming the flower buds.

Notes in cultivation:—When grown side by side under full sun in a non-watered, non-wind protected garden, A. bullatus thrives well, as it does in its native dry coastal forests even under sea-spray ( Gâteblé 2015), while A. mesophilus stagnates in growth, since it is usually found in deep, well-watered soil, sheltered from the sun and wind, at least in its early stages of development.

Etymology:—The plant is named after the mesic forests where it grows.

Species recognition:—With its large leaves, entire or rarely trilobed (juvenile leaves) and its general architecture, Acropogon mesophilus is a species that could only be confused with two others, A. bullatus and A. veillonii . Table 1 compares the main characteristics of these three species. The leaf blade is generally flat in A. mesophilus while generally strongly bullate in A. bullatus and weakly bullate in A. veillonii , blade shape is generally oval in A. bullatus and A. veillonii while ovate in A. mesophilus , with generally 3 main palmate veins in A. mesophilus versus generally 5 main palmate veins in the two other species. Flower color of this new species is intermediate between A. veillonii , which has yellow flowers with sometimes some red at the base of the calyx, and A. bullatus , which has red flowers with some yellow at the edges ( Fig. 2 D–E & G–H ). The follicles of the fruit have a smooth surface in A. bullatus and A. mesophilus , versus coarse in A. veillonii . There is no overlap in the ecology or distribution of these three species, with A. veillonii being restricted to some rainforests on calcareous substrates of the Loyalty Islands and East coast of Grande-Terre, A. bullatus occurring on some coastal dry forests, or littoral forests South of Poya on the West coast of Grande-Terre and Isle of Pines, and with A. mesophilus only known from some rare inland mesic forests between Boulouparis and La Foa ( Fig. 3 ).

sp. nov. and A. veillonii .

Conservation status:—With an Extent of Occurrence (EOO) of 24 km 2, an Area of Occupancy (AOO) of 20 km 2, and three subpopulations, all occurring outside of protected areas and with strong herbivore pressures [as detailed in Discussion], Acropogon mesophilus is assigned a preliminary status of Endangered (EN B1ab[i,iii,iv] + B2ab[i,iii,iv]) based on the IUCN Red List Categories and Criteria ( IUCN 2012).

Additional specimens examined (Paratypes):— NEW CALEDONIA. Province Sud: Boulouparis, Ouaménie , 55 m, 21°49’08.18”S, 165°56’55.78”E, 17 November 2011, Gâteblé (leg. Létocart, Fogliani & Ounémoa) 41 (NOU-082672!) ; ibid. loc., 30 March 2012, Munzinger, D. & I. Léocart, & Dubreuil 6721 ( NOU082939 !) ; ibid. loc., 2 October 2014, Gâteblé, Barrabé, Fleurot, Létocart & Ounémoa 545 (NOU-081993!) ; La Foa, Pocquereux , 150–200 m, 21°46’18.76”S, 165°56’29”E, 6 October 2014, Le Borgne 58 (NOU-052036!) ; ibid. loc., 13 July 2013, Le Borgne 57 (NOU-083466!, NOU-083467!, NOU-083468!, P!) ; Boulouparis, Ouaménie , bord de piste, 23 October 2014, Butin 135 (NOU-084125!, P!) ; Camp Brun , le long de la Diahot, 180 m, 21°48’55.84”S, 165°55’09.70”E, 19 May 2015, Gâteblé, Anger & Ounémoa 685 (NOU-081991!, NOU-081992!, P!) ; Camp Brun , le long de la Diahot, 130 m, 21°49’29.85”S, 165°54’50.71”E, 19 May 2015, Gâteblé 686 (MPU-028532!) ; ibid. loc., 17 November 2015, Gâteblé 719 (MPU-028531!, NOU-081990!, P!) ; Camp Brun, en contrebas de la maison de M. Laven , 110 m, 21°49’44.21”S, 165°54’46.76”E, 30 April 2016, Gâteblé & Deschamps 776 ( NOU!) .

Discussion:—During field work, feral pigs (Sus scropha) and invasive deer ( Rusa timorensis ) populations were regularly observed in these mesic forests. In all populations surveyed, there were no young Acropogon trees observed, only adults. Lack of regeneration is likely due to the strong herbivore pressures from deer and pig overabundance. This observation is also true for most of the species growing along with this new species. Some rat predation of immature fruits and seeds directly on the trees was also observed (see predation marks on fruits of Gâteblé et al. 685), and black rat ( Rattus rattus ) predation of fruits is reported to be a threat for most Acropogon species, especially on A. bullatus (F. Brescia, pers. comm.).

Figures

FIGURE 1.—Acropogon mesophilus Munzinger & Gâteblé spec. nov. A. Flowering branch B. Details of domatia on abaxial leaf surface. C. Inflorescence. D. Female flower. E. Male flower. F. Infructescence. G. Detail of an open follicle. A–E, Le Borgne 58 (NOU), F–G, Le Borgne 57 (NOU). Drawings by Laurence Ramon.

FIGURE 2.—Acropogon mesophilus Munzinger & Gâteblé spec. nov. (A–F), A. bullatus (G) & A. veillonii (H): A. Overview of a single big tree. B. Flowering branch. C. Leaves. D. Inflorescence. E. Male (left) and female (right) flowers. F. Follicles. G–H. Inflorescences. Gâteblé 711 (A–B), Gâteblé et al. 685 (C), Gâteblé 719 (D), Le Borgne 58 (E–F), Gâteblé & Butaud 733 (G), photos by G. Gâteblé (A–D & G), T. Le Borgne (E–F) & J.-F. Butaud (H).

FIGURE 3.—Distribution of Acropogon bullatus (circles), A. mesophilus (triangles) and A. veillonii (squares) in New Caledonia. Grey fill indicates ultramafic substrate, crosshatch fill indicates calcareous substrates. Protected areas are in dotted fill. Black symbols indicate localities from herbarium specimens [from specimens at G, NOU and P], while gray symbols indicate localities from observations, without voucher specimens [from Butaud (2014) for A. veillonii, Suprin (2008) for A. bullatus, and T. Le Borgne (pers. comm.) for A. mesophilus]. Localities for specimens from herbarium G gathered from GBIF.org.