Alyxia humboldtensis Lannuzel & Gâteblé, 2024

Lannuzel, Guillaume, Munzinger, Jérôme, Vandrot, Hervé & Gâteblé, Gildas, 2024, Alyxia Banks ex R. Br. in New Caledonia: a clarification of several species complexes, nomenclatural notes, and a description of three new species, Phytotaxa 649 (1), pp. 1-43 : 11-13

Alyxia humboldtensis Lannuzel & Gâteblé , sp.nov. ( Figs. 4 , 5 ), (urn:lsid:ipni.org:names: 77336418-1)

Diagnosis:— Alyxia humboldtensis is a small procumbent vine characterized by its leaves, generally in whorls of 4–5. It is similar to A. leucogyne in being the only species with more than 3 leaves per whorl, but differs from it by the adult plant’s size, sessile leaves, short and reduced inflorescences and apparently glabrous fruits. Flowers are twice as long (ca. 8 mm vs 4 mm in A. leucogyne ), with yellowish corolla (white in A. leucogyne ).

Type:— NEW CALEDONIA, South Province, Mont Humboldt , elev. 1500 m, 21°52'58"S, 166°25'19"E, 2 February 2022, Lannuzel & Pouget 568, holotype: NOU [ NOU108492 !] ; isotype: P [ P01139694 !]

Procumbent liana, up to 50 cm, stems covered by ca. 0.1 mm hairs; latex white. Leaves verticillate in whorls of 3–5, coriaceous, green adaxially, light green abaxially, strongly revolutate, sessile, lamina oboval to spatulate, 24–27× 13–18 mm; base attenuate to rounded, apex retuse, mucronate, both surfaces minutely pubescent, covered with 0.1 mm hairs, leaf venation not visible apart from the midrib. Flowers axillary, grouped in reduced dichasial cymes, axes green, sparsely pubescent, ca. 1.3 mm, pedicels null to ca. 0.5 mm. Narrowly triangular bracts, ca. 2.5 × 1 mm, green, margin ciliate.

Flower 5-merous, 7.8 × 1.8 mm. Calyx lobes slightly spreading from corolla, narrowly triangular, acute at apex, ca. 3.5 × 1 mm, green, glabrous, with margin ciliate toward apex. Corolla pale yellow, tube ca. 4.5 × 1.5 mm, glabrous outside, with only 1 ring of hairs inside, below anthers and stigma, composed of 0.1 mm long appressed hairs, lobes sinistrorse, lanceolate, glabrous, erected at anthesis.

Anther cone 1 mm long, not exserted; filaments 0.2 mm long, inserted at 2/3 of tube length. Ovary ca. 0.6 × 0.5 mm, very hairy around base with 0.2–0.3 mm long hairs, style 1.5 mm long, glabrous, stigma ovoid, acute, hairy at top. Mature fruit unknown. From young fruits, mericarps seem to present 1–2 ovoid articles.

Distribution and habitat: — Alyxia humboldtensis is known from only one population, located near the Mont Humboldt summit, at 1500 m elev. It grows as a procumbent liana in the cyperaceous vegetation between peridotite rocks.

Phenology:— From herbarium specimens and pictures available, the species seems to flower in December and January. Immature fruits were seen in February.

Etymology:— The species is named after the mountain where the only population is known, Mont Humboldt.

Specimen examined:— NEW CALEDONIA: South province; Mont Humboldt , elev. 1500 m, 21°52'58"S, 166°25'19"E, 13 December 2013, Gâteblé. 410 ( NOU092221 !) .

Figures

FIGURE 4. Alyxia humboldtensis, with detail of immature fruits (A), flowers (B), habit (C), and a flowering branch (D). Photographers: G. Lannuzel (A & C from Lannuzel & Pouget 568), C. Laudereau (B & D).

FIGURE 5. Known distribution of Alyxia dolioliflora (dots) and Alyxia humboldtensis (squares). Symbols with “T” represent type specimens. Grayed areas represent ultramafic substrates.