Psychotria nigotei Barrabé, 2014

Barrabé, Laure, 2014, Four new species of Psychotria (Rubiaceae) from New Caledonia, including one presumed to be extinct, Phytotaxa 173 (2), pp. 101-116 : 109-112

Psychotria nigotei Barrabé , sp. nov. ( Figs. 6 , 7 )

This species is similar to Psychotria poissoniana ( Baillon 1879: 230) Guillaumin ex Moore (1921: 338) , from which it differs principally by being a creeping shrub (vs. slender shrub in P. poissoniana ), and by its bullate and densely hirsutulous to tomentose leaf blades (vs. flat, and glabrous to hispid), and by the secondary inflorescence axes that are <1 cm long (vs.> 1 cm long).

Types: — NEW CALEDONIA. Grande Terre, Province Sud: Païta , flanc est du Mont Mou, maquis ligno-herbacé de crête, susbtrat ultramafique, péridotites, sol ferrallitique ferritique, 800 m, 22°3’39’’S, 166°21’49’’E, 4 November 2009, L. Barrabé & F. Rigault 981 (holotype P!, isotypes K!, NOU-034119!, S!, Z!) .

Saxicolous, creeping shrub, sparsely branched, 20–40 cm tall; bark gray and dark brown when dry, glabrous, wrinkled; young shoots, petioles and terminal vegetative buds hirsutulous to tomentose, trichomes red-brown when dry. Stipules free, triangular to ovate, 6–7.5 × 3–5 mm, with margins fimbriate to laciniate, green, hirsutulous to tomentose, trichomes red-brown when dry, semi-deciduous; colleters not seen. Leaves clustered at ends of branches; petioles smooth, 0.6–1.2 cm long, 1.5–2 mm thick, plano-convex; blades elliptic to ovate (sometimes slightly obovate), 3–10.1 × 2–4.4 cm, round to obtuse (sometimes slightly acute) at apex, acute at base, margins entire and slightly revolute, blades chartaceous, bullate, discolorous when dry, darker on adaxial side, hirsutulous to tomentose on both sides, trichomes white when dry; midvein and secondary veins tomentose, midvein raised on adaxial side, flat on abaxial side; secondary veins 7–10 on each side, spaced at 3–11 mm, at 40–70° angle with the midvein, raised on adaxial side, flat on abaxial side; tertiary venation obscure on adaxial side, reticulate on abaxial side. Inflorescences erect, subcapitate, 9–21-flowered; rachis hirsutulous to tomentose, trichomes white when dry, primary axis 5.5–14 mm long, 1–2 mm thick, secondary axes 4–10 mm long, 1–1.5 mm thick. Bracts axillary, 2 per secondary axis, 2 per flower, linear, 2.5–5 mm long, acute at apex, with slightly fimbriate margins, pale green, hirsutulous to tomentose, trichomes white when dry on both sides. Flowers 5-merous, erect, sessile, heterostylous; flower buds obovoid. Hypanthium turbinate, 1.5 × 1.7–2 mm, smooth, green, densely tomentose, trichomes white when dry; nectary disk entire, circular, to 1.5 mm in diameter, glabrous, papillose. Calyx chartaceous, pale green, hirsute outside, glabrous inside; tube to 1 mm long, colleters lacking; lobes triangular, 0.25 × 1.5 mm, obtuse with an apiculus at apex, erect, margins entire. Corolla actinomorphic, funnel-form, spongy, white, apex and inner margins of lobes bluish-gray, hirsutulous outside, glabrous inside except a hairy ring of 2 mm below the mouth; tube 7–9.5 mm long, 1.5–2.5 mm wide at base, 3–5.5 mm wide at mouth; lobes lanceolate, 4–6.5 × 1.5–2.5 mm, acute and corniculate at apex, erect to perpendicular to the tube (at anthesis), adaxial and abaxial sides smooth. Stamens exserted, glabrous; filaments linear, ca. 2–5 × 0.5 mm, terete, white, fused to the corolla mouth; anthers ovoid, ca. 1.75 × 0.5 mm, bluish-gray, dorsifixed. Style filiform, 11 × 0.5 mm, terete, white, glabrous. Stigma bilobed, white, papillate; lobes ovoid, 1–2 mm long. Fruits ellipsoid, 4–6.5 × 4–4.5 mm; exocarp smooth, bluish-black, ribbed when dry, hirsute; mesocarp unknown. Pyrenes plano-convex, ellipsoid, 5 × 1.5 × 3 mm, obtuse at apex, round at base; dorsal side convex, strongly wrinkled, 5-ribbed; ventral side flat, wrinkled, with a thin raised median crest; pregermination slits lacking, basal aperture present; exotesta reddish brown. Endosperm 5-ribbed, not ruminate, cream-white, ethanol-soluble seed coat pigment lacking.

Distribution and habitat: — Psychotria nigotei Barrabé (this publication) occurs in ‘maquis minier’, on peridotitic rocky crests. The five herbarium specimens of this species were collected in two areas, Haute Tontouta and Mount Mou, at 800–900 m elevation, in the district of Païta ( Fig. 3 ). This species can be considered as a microendemic, as it occurs at only two localities which are close to one another.

Phenology: —This species is too poorly known for any conclusions to be made regarding its flowering and fruiting periods. However, specimens with flowers in bud and at anthesis were collected in November, and specimens in fruit in February and April.

Etymology: —This species is named for Williams Nigote, who has been a botanist at the IRD Nouméa for the last 10 years.

Affinities: — Psychotria nigotei belongs to the ‘ poissoniana’ subclade (Barrabé 2013), which includes four other species: P. leratii Guillaumin (1929: 119) , P. poissoniana , P. pubituba Moore (1921: 337) , and another new species, not yet described. These five species have all leaves more than 3 cm long and generally hirsute, bifurcate or laciniate stipules, bluish to whitish inflorescences rachises, bluish-gray to bluish-white corollas, and black to bluish-black fruits, more than 0.5 cm in diameter. However, P. nigotei differs from the other members of the group by being a creeping shrub (vs. erect shrubs), with leaf blades 3–10.1 × 2–4.4 cm (vs. generally 10–25 × 3–10 cm), bullate (vs. flat), densely hirsutulous to tomentose (vs. glabrous, sparsely hirsute to hispid), inflorescences with reduced secondary peduncles, less than 1.5 cm long (vs. secondary peduncles robust, more than 1.5 cm long), white corolla (vs. bluish-gray), and the dorsal side of the pyrenes without a cavity (vs. with one to two cavities delimited by curved margins). In addition, the other four species of the subclade occur throughout the main island and are generally found in or at the edges of rainforests, whereas P. nigotei is found strictly in ‘maquis minier’ on ultramafic substrates, and it occurs at only two locations in the south-eastern part of the island ( Fig. 3 ).

Conservation assessment according to the IUCN Red List categories and criteria: — Psychotria nigotei is known from only two localities: the protected area of Mount Mou, and Haute Tontouta. It might occur also on other nearby ultramafic summits in southern New Caledonia, but I have seen no specimens to confirm this. The areas of Mount Mou and Haute Tontouta, above 800 m do not exceed 70 km ²; therefore both area of occupancy and extent of occurrence, as defined by the IUCN (2012), are much smaller than this. The former location has been subject in the past to nickel mining activities and intensive mining currently occurs in parts of the upper Tontouta valley. The species is therefore threatened by the impact of mining (dumping of mining waste, opening of roads; Jaffré et al. 1998a) and by fire, as each year fires degrade significant portions of the south-eastern part of the main island of New Caledonia ( Jaffré et al. 1998b). Consequently, I assign a provisional status for P. nigotei of Critically Endangered: CR B1ab(i,ii,iii) + 2ab(i,ii,iii).

Paratypes: — NEW CALEDONIA. Grande Terre, Province Sud: Païta , flanc est du Mont Mou, 800 m, 22°3’39’’S, 166°21’49’’E, 4 November 2009, L. Barrabé & F. Rigault 982 (NOU-034120!, P!); Haute Tontouta, 900 m, 11 November 1950, M.G. Baumann-Bodenheim 8082 (P-00752137!, second label ‘8083’); Mont Mou, 880 m, 22°3’39’’S, 166°21’49’’E, 10 February 2009, C. Grignon, F. Rigault & V. Apiazari 168 (NOU-049815!, P!, S!); mont Mou, 22°33’7’’S, 166°20’2’’E, 2 April 2009, C. Grignon & J. Munzinger 255 (NOU-050287!, NOU-050305!) .

Figures

FIGURE 3. Distribution map of the four new Psychotria species in New Caledonia. Ultramafic substrates are shaded in gray.

FIGURE 6. Psychotria nigotei Barrabé. A. Branches with inflorescences and flowers at anthesis; B. Detail of the adaxial leaf apex; C. Stipule; D. Detail of the calyx; E. Flower at anthesis; F. Stigmas; G. Details of stamens; H. Cross section of the pyrene; I. Dorsal face of the pyrene; J. Lateral surface of the pyrene; K. Ventral face of the pyrene. Drawn by Michèle Magat.

FIGURE 7. Psychotria nigotei Barrabé. A. Habit; B. Young fruits; C. Flowers at anthesis. Photos credits: Céline Grignon (B); Frédéric Rigault (A, C).