Oxyrhynchus margueriteae Munzinger & Fleurot, 2024

Munzinger, Jérôme & Fleurot, Dominique, 2024, Novitates neocaledonicae XVI: Oxyrhynchus margueriteae sp. nov. (Fabaceae), a new species endemic to New Caledonia, and the first record of the genus in the territory, Adansonia (3) 46 (22), pp. 239-246 : 241-244

Oxyrhynchus margueriteae Munzinger & Fleurot , sp. nov.

( Figs 1 ; 2 )

DIAGNOSIS. — Among species of Oxyrhynchus , the new species most closely resembles O. trinervius (Donn.Sm.) Rudd because of its calyx lateral lobes ovate to broadly ovate, its flowers 10- 14 mm long and its (sub)glabrous fruit. However, in Oxyrhynchus margueriteae sp. nov., the bases of the lower lips are not overlapping (vs overlapping), the flower pedicels are shorter (2-6 mm vs 8-15 mm), the fruit is shorter and less wide (3.75-5.75 cm × 1.4-2 cm vs 7-11 × 3-4 cm), and the seeds fewer (1-3 vs [2]3-5) and smaller (7-8 × 6-7 mm, 4.5-5 mm thick versus 13-16 × 11- 15 mm, 12-14 mm thick).

TYPE MATERIAL. — New Caledonia • Province Nord, Plateau de Tango; 20°56’30.5”S, 165°6’36”E; 6.VII.2010; fr.; J.-P. Butin leg.; Munzinger 6047; holo-, P [ P02857426 ]!; iso-, NOU [ NOU079486 ]!, P [ P02857425 ]!).

PARATYPI. — New Caledonia • Poindimié , Hoeênè; 20°56’37.184”S, 165°06’43.541”E; alt. 150 m; 22.VIII.2021; Fleurot 912; j.fr.; para-, MPU [ MPU313240 ], NOU [ NOU091995 , NOU107965 ], P [ P01139479 ]) • ibid.; 20°56’36.893”S, 165°06’43.367”E; alt. 142 m; 12.VI.2022; fl. buds; Fleurot 938; para-, NOU [ NOU092404 , NOU108628 ] (alc.), P [ P01139662 ] • Tango ; [20°56’37”S, 165°06’42”E]; 15.VI.2009; fl.; J.-P. Butin leg.; J. Fambart-Tinel 207; para-, NOU [ NOU050883 ] .

PHENOLOGY. — Buds and open flowers observed in June, fruit in July and August.

HABITAT. — Oxyrhynchus margueriteae sp. nov. grows in low to medium-altitude dense rainforest (sensu Jaffré et al. 2012), on volcano-sedimentary substrate, between 115 and 150 m altitude. It was observed in a canopy around 25-30 m high, among other lianas, notably Tetracera billardierei Martelli ( Dilleniaceae ), Hugonia jenkinsii F.Muell. ( Linaceae ) and Piper sp. ( Piperaceae ). The tallest liana observed is growing on Elaeocarpus angustifolius Blume ( Elaeocarpaceae ).

DISTRIBUTION. — The plant appears to be endemic to the Northern Province of New Caledonia ( Fig. 3 ). It is known only from a single forest in a small valley at the confluence of the Hoeênè river (Tango region, Bopope tribe).

CONSERVATION STATUS. — Oxyrhynchus margueriteae sp. nov. is only known from a small valley of just over 12 hectares, which contains in its talwegs a relic of dense rainforest covering 5.4 hectares, of which 2.4 ha were surveyed (c. 45%) ( Fig. 4 ). In the western part of the valley, less than one hectare is covered by a former plantation of Pinus caribaea Morelet (Caribbean pine), while the other slopes and ridges are essentially covered by niaoulis savannah with many common ferns (genus Lygodium Sw. ). These two secondary environments seem unfavorable to the presence of the liana, which has a forest ecology. As of June 12, 2022, the date of the Fleurot 938 collection, six fertile adult lianas and 1 juvenile liana have been observed and mapped. The main threats to this population are the overabundance of pigs and deers, and anthropogenic fires. Thus, as there are fewer than 50 known mature individuals, we assign O. margueriteae , sp. nov. a preliminary status of “Critically Endangered” (CR) according to criterion D.

VERNACULAR NAME. — Unknown.

ETYMOLOGY. — The plant is dedicated to Marguerite Butin, wife of Jean-Pierre Butin, the plant's discoverer. She was very supportive of his hobby, letting him spend most of his free time scouring the territory for rare plants.

DESCRIPTION

Liana measuring up to 12 cm in diameter at the base and reaching heights of over 20 m, with translucent latex when first bled, then oxidizing to red (a few tens of seconds), not very abundant, gray bark streaked with crevices. Leaves trifoliolate, stipulate, leaflets weakly acuminate, terminal leaflet ovate or broadly ovate, symmetrical (52-)57-70(-85) mm long, (40-)42- 48(-67) mm wide, terminal petiolule 19-21 mm long, with a few appressed hairs directed towards the apex, apical pulvinus 4 mm long, hirsute, curved at 90°, stipels narrowly triangular, c. 1 mm long, lateral leaflets broadly oval, very asymmetrical (50-)54-67(-77) mm long, (35-)37-45(-55) mm wide, petiole reduced to a pulvinus 2.5-4 mm long, stipels oblong, 1-2 × 0.5-1 mm, primaries and secondaries veins beige, abaxially prominent, narrower and less prominent adaxially, 2-3 pairs of secondaries, inter-secondaries frequent. Petiole 40-80 mm long, triangular stipules 2 mm long, blackish in herbarium, glabrous or sparsely hairy.

Axillary inflorescence about 11 cm long, up to 33 cm, with flattened inflorescence axis, up to 3 mm wide, hairy in terminal part with long white hairs up to 0.5 mm long, appressed towards apex, glabrescent in basal part, inflorescence a compound raceme with condensed partial inflorescences, with 3 to 20 flowers, irregularly spaced from 5 to 19 mm. Bracts lanceolate, 2 mm long, variegated with black.

Flower bud broadly rounded-truncated, laterally flattened, 6-8 mm long. Flower papilionaceous, 10-14 mm long, mauve with bluish tints, base of petals whitish (in vivo), pedicel 2-6 m long,with hirsute white hairs.Calycle with 0-2 oval bracts, rapidly caducous, veined, 1-1.5 mm long, with ciliated membranous margin, beige, adaxial side weakly tomentose, abaxial side glabrous; calyx campanulate with 5 subequal lobes, as long as the tube; lobes not overlapping, green, rounded, 1. 5 × 1.5 mm for the lower three, 1.5 × 2.0 mm for the upper two, inner surface sericeous, margin ciliate, outer surface subglabrous. The standard bilobed, 12.5-17 mm wide, 7-8.5 mm high, wings broadly obovate to suborbicular, 7-12 mm long × 5-8 mm wide, mitered 3.5-5 mm, petals of keel fused, at least apically, rostrate, with suborbicular central part c. 5 mm in diameter, and tips tapering 3-4 mm. Androecium diadelphous, 9 stamens 11-13 mm long, fused by their filaments, free filament over 3-5 mm of their length, 1 free stamen, c. 10 mm long.Anthers 0.7-1.0 mm long × 0.3-0.4 mm wide, basifixed.Gynoecium c. 15 mm, ovary c. 5 × 0.8 mm, with suture line covered by a line of sericeous hairs, ovary long attenuated into a glabrous style or with a few long hairs scattered at the apex, stigma punctiform.

Legume oblong 37.5-57.5 mm long (in vivo), 13.6-20 mm wide, sparsely pubescent towards apex, becoming glabrous, perianth caducous, pedicel 7-11.8 mm long × 1-1.4 mm diameter. Valves twisting at opening, brown on the outside, white and glabrous on the inside. Seeds 1-3 per legume, black (immature), prismatic spherical, 7-8 × 6-7 mm, 4.5-5 mm thick, with beige hilum forming a bead on one-half to one-third of the circumference.

Figures

FIG. 1. — Oxyrhynchus margueriteae sp. nov.: A, flowering shoot; B, flower (front view); C, calyx (side view); D, calyx (top view); E, keel; F, wing; G, standard; H, androecium (side view); I, gynoecium (side view); J, fruiting shoot; K, legume; L, seed (dorsal view); M, seed (lateral view); M, seed (ventral view). Scale bars: A, J-N, 1 cm; B, 4 mm; C-I, 1 mm. Illustration by Roger Lala Andriamiarisoa.

FIG. 2. — Field pictures of Oxyrhynchus margueriteae sp. nov.: A, trunk, partially necrotic (© C. Laudereau); B, slash (© D. Fleurot); C, shoot and Jean-Pierre Butin (© D. Fleurot); D, abaxial side of a leaf (© D. Fleurot); E, flower (© J.-P. Butin); F, petiole insertion with stipule (© C. Laudereau); G, fruits (© D. Fleurot).

FIG. 3. — Distribution of Oxyrhynchus margueriteae sp. nov. in New Caledonia, with vegetation types (after Jaffré et al. 2012): Grey, sclerophyll forest, wetland and coastal vegetation; dark green, low and medium altitude humid dense forests; light green, high altitude maquis and forest; brown, maquis on ultramafic substrates; beige, Savannahs and secondary thickets. Zoom on Bopope area, with ultramafic substrates in beige.

FIG. 4. — Presence map of known living individuals (yellow dots), and the type that has not been relocated, probably dead (black cross) of Oxyrhynchus mar- gueriteae sp. nov. In yellow, the total watershed of the small valley, in green, the surface area of the rainforest, in white, the surveyed area, in dashed orange, an area planted with Pinus caribaea Morelet.