Marsdenia guillauminiana (P.T.Li) Meve, Gâteblé & Liede 2017

Meve, Ulrich, Gâteblé, Gildas & Liede-Schumann, Sigrid, 2017, Taxonomic novelties in Apocynaceae subfam. Asclepiadoideae from New Caledonia, Adansonia 39 (1), pp. 55-70 : 69

Marsdenia guillauminiana (P.T.Li) Meve, Gâteblé & Liede , comb. nov.

Tylophora guillauminiana P.T. Li , Journal of South China Agricultural University 15 (1): 64 (1994), replacement name for Tylophora micrantha Guillaumin , Bulletin du Muséum national d’histoire naturelle, sér. 2, 16: 82 (1944), nom. illeg.

TYPUS. — New Caledonia. Grande-Terre, North Prov., Balade , 1861- 1867, E.Vieillard 987 (holo-, P [ P00607353 ]! ; iso-, P [ P04258524 ]!) .

ETYMOLOGY. — This species is named after André Guillaumin (1885-1974), author of the Flore analytique et synoptique de la Nouvelle-Calédonie ( Guillaumin 1948).

DISTRIBUTION AND HABITAT. — New Caledonia. Grande-Terre, North Prov.

CONSERVATION STATUS. — Known from the type collection over 150 years ago, only, and possibly extinct.

DESCRIPTION

Plants

Ascending, twining, 6-10 m tall.

Shoots

Perennial, herbaceous, glabrous; internodes 3.5-5 cm long, 1.5-2 mm diam.

Leaves

With 10-15 mm long petioles, blades with 4 colleters at the base, herbaceous to coriaceous, 3-4.5 × 2-2.8 cm, elliptic, basally rounded, apically obtuse or minutely mucronate, glabrous on both sides.

Inflorescences

Always one per node, extra-axillary, forming a basal dichasium bearing two sciadioids, 10-20-flowered, all flowers open synchronously.

Peduncles

10-15 mm long, glabrous.

Flowers

With pedicels 2-3 mm long, glabrous.

Flower buds

c. 1.5 × 1 mm when mature, globose.

Calyx

Entirely free; lobes c.1 x. 0.7 mm, ovate, apically acute.

Corolla

Rotate-campanulate, 1.5-2 mm long, c. 2.5 mm diam., adaxially with to 200 µm long trichomes on apical and lateral parts of the lobes; lobes fused about half of total corolla length, 0.6-0.7 mm wide, patent, ovate, apically acute.

Gynostegial corona of free staminal lobes

Glabrous, c. 0.6 mm long, shorter than the gynostegium; lobes laminar, oblong.

Gynostegium

c. 0.7 mm long, c. 0.6 mm diam., elevated by a column of c. 200 µm length; anthers broader than long, rectangular, abaxially planar, forming a basal arch; anther wings c. 300 µm long, extending along the whole length of the anther; anther wings of adjacent anthers parallel to each other, in the same plane as the anther; connective appendages c. 400 × 300 µm, ovate, slightly inflexed.

Pollinarium

Corpusculum c. 140 × 55 µm, elliptic; caudicles c. 30 µm long, medianly inserted at the corpusculum, cylindrical, straight, horizontal; pollinia apically attached to the caudicles, erect, c. 200 × 50 µm, round in cross-section, oblongoid.

Style-head

c. 0.35 mm long, c. 0.6 mm diam.; upper part 0.1 mm long, shorter than the lower part, umbonate.

Fruits and seeds

Not seen.

REMARKS

Known only from the type. The very small flowers with their small pollinaria and the open, zig-zagging inflorescences at first point to Tylophora / Vincetoxicum as generic relationship of this rare species. However, repeated study of gynostegial structures showing: 1) a fringe-like corona also in interstaminal position; 2) prominent anther wings (as in Marsdenia neocaledonica , sp. nov., M. tylophoroides or M. variifolia ); and 3) pollinaria with strictly erectly positioned, oblongoid pollinia, finally point to Marsdenia as only possible relationship for this element.

This species and Tylophora anisotomoides Schltr. have been usually regarded as synonymous (cf. to http://www.endemia. nc, https://plants.jstor.org/). However, this is clearly incorrect as the protologue of T. anisotomoides gives glabrous corolla lobes, but Vieillard 987, the type and only original material of Tylophora micrantha , possesses trichomes on the adaxial side of the corolla lobes. In addition, Schlechter’s (1906) statement in the protologue of T. anisotomoides “ coronae foliolis tubo staminum basi alte adnatis carnosis, lanceolato-rhomboideis ” unambiguously refers to a character highly significant for Vincetoxicum biglandulosum but not for Tylophora micrantha where the corona lobes are neither basal nor rhomboid nor carnose. Schlechter (1906) also compared his new species with Tylophora tapeinogyne as being most similar – the latter is a long-established synonym of T. biglandulosa . Finally, all further non-type specimens in P labelled “ Tylophora anisotomoides ” are found to belong to small-flowered or sterile material of Vincetoxicum (Tylophora) biglandulosum (cf. https:// science.mnhn.fr/institution/mnhn/collection/p/item/search, last access on 3.XI.2016).