Marsdenia weberlingiana 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 : 68

Marsdenia weberlingiana Liede , sp. nov.

( Fig. 7 )

A twining herb with ovate, coriacous and discolorous leaves indistinguishable from M. nigriflora by vegetative characters, but otherwise unique within New Caledonian Marsdenia species because of its radiate flowers of around 12 mm diam. with adaxially glabrous corolla lobes, bipartite staminal corona lobes differentiated into a swollen, transversally ovate base and a lingulate apical part. The style-head is subconical and slightly papillate, and thus very similar to the one of M. nigriflora .

TYPUS. — New Caledonia. Grande-Terre, North Prov., Hô ( Houaïlou ), reste de forêt sur terrain serpentineux altéré, 50 m, 29.IV.1973, H.S.MacKee 26650 (holo-, P [ P00607351 ]! ; iso-, P [ P00607352 ]!) .

ETYMOLOGY. — Named after the late Prof. Focko Weberling (University of Ulm, Germany), well-known morphologist and inflorescence specialist. Weberling, highly respected teacher and mentor of S. Liede-Schumann, would have celebrated his 90th birthday in March 2016.

DISTRIBUTION AND HABITAT. — New Caledonia. Grande-Terre, North Prov. Known only from the type collection ( Fig. 3 ). Margins of disturbed rainforest on serpentine; 50 m.

CONSERVATION STATUS. — So far, the only known locality of this new species is at Hô, just north of Houaïlou. The col de Hô region and the Cap Bocage peninsula are renowned for several rare species despite a general lack of botanical knowledge for the area. As a whole this region could be considered as an “ultramafic island”. Most of the area is under nickel mining concession and the Cap Bocage peninsula is under active mining. The other main threat in this region are the severe bush fires that frequently occur. The North Province “Nature Guard” Philippe Nekotrotro has recently surveyed the type locality for this species without success. Considering that the remnants of rainforest pockets in the area are under fire and mining pressure, M. weberlingiana Liede , sp. nov. is assigned a preliminary IUCN conservation status of “Critically endangered” [CR B1ab(i,ii,iii,v)+2ab(i,ii,iii,v)] using Red List criteria ( IUCN, 2012) if not Extinct.

DESCRIPTION

Plants

Ascending, twining.

Shoots

Perennial, herbaceous, glabrescent, sparsely covered with appressed trichomes, 250-300 µm long; internodes 6-10 cm long, 2-2.5 mm diam.

Latex

Colorless fide MacKee 26650. Leaves with petiole 10-15 mm long, leaf blades coriaceous, with 2-4 colleters at the base, 70-100 × 30-45 mm, elliptic, basally rounded, apically acuminate with acumen 4-7 mm long, discolourous, glabrous on both sides.

Inflorescences

Always one per node, extra-axillary, 5-12 -flowered, all flowers open synchronously, sciadioidal. Peduncles 12-15 mm long, sparsely covered over the whole surface with appressed, 250- 300 µm long trichomes.

Flowers

With floral bracts 1 mm long, 0.6 mm wide at the base, ovate, with scattered trichomes. Pedicels 10-15 mm long, sparsely covered over the whole surface with appressed trichomes, 150- 200 µm long. Flower buds 7 × 4 mm when mature, ovoid.

Calyx

Fused for almost half of its length, campanulate, ciliate; lobes 2.5 × 1.5 mm, ovate, apically obtuse.

Corolla

Rotate, 6 mm long, abaxially green, adaxially brown to purple; lobes basally fused, 2.5-3 mm wide, horizontal, oblong, apically obtuse, marginally ciliate.

Gynostegial corona of free staminal lobes

Purplish-red, glabrous, 1.4-1.5 mm long, equalling to or longer than the gynostegium; lobes solid, massive, basally oblongoid, apically subulate, extended into a long, slender tip.

Gynostegium

c. 1.5 mm long, 0.7 mm diam., sessile. Stamens without filament; anthers broader than long, trapezoidal, abaxially planar; anther wings 450 µm long, extending along the whole length of the anther, consisting of distal ridge alone; anther wings of adjacent anthers parallel to each other, in the same plane as the anther; connective appendages c. 700 × 700 µm, triangular, equalling the stamen in width, strongly inflexed.

Pollinarium

Corpusculum c. 500 µm long, more than twice as long as broad, elliptic, margins of the corpuscular cleft parallel; caudicles c. 625 µm long, (sub-)basally inserted at the corpusculum, cylindrical, s-shaped, convex-concave, not thickened at the insertion of the pollinium; pollinia apically attached to the caudicles, erect, c. 450 × 200 µm, ovate in cross-section, ovoid.

Style-head

Slightly papillose, c. 0.5 mm long, c. 1 mm diam.; upper part c. 0.25 mm long, equalling the lower part, depressed-conical.

Fruits and seeds

Unknown.

REMARKS

The generic placement of this new species left some questions due to its unusual character combination. Unfortunately, the condition of the herbarium specimens was not sufficient to extract DNA for molecular analysis, so that the relationships could not be tested molecularly. Originally thought to belong to Sarcolobus R.Br. (cf. labels on type specimens), because of geniculate caudicles and a papillate style-head surface (cf. Forster 1991), this element is nevertheless published under Marsdenia , here. Latex constitution supports this placement, as colorless and clear instead of the predominant milky latex is a feature not rarely found in Marsdenia ( Forster 1995b) , especially in New Caledonian species (e.g. M. ericoides Schltr. , M. koniamboensis Guillaumin ). Colorless latex, in contrast, is not known to occur in Sarcolobus (cf. Forster 1991). Also, Marsdenia weberlingiana Liede , sp. nov. is not only indistinguishable from M. nigriflora Guillaumin with regard to vegetative characters, it shares a radiate corolla (but of 12 mm diam. versus 5 mm diam. in M. nigriflora ), a more or less papillate style-head surface and similar pollinaria. However, pollinaria are larger in M. weberlingiana Liede , sp. nov. and with more distinctly geniculate caudicles. Geniculate caudicles, though fairly short ones, also occur in M. kaalaensis , sp. nov. ( Fig. 2E ).

Figures

FIG. 7. ─ Marsdenia weberlingiana Liede, sp. nov.: A, branch with inflorescences; B, flower, top view; C, flower, side view, corolla partially removed; D, gynostegium; E, pollinarium; F, style-head. Drawings: U. Frensch from M. MacKee 26650 (P). Scale bars: A, 2 cm; B, 3 mm; C, 2 mm; D, 1 mm; E, 0.5 mm; F, 0.2 mm.

FIG. 3. ─ Distribution of the five new Neo-Caledonian Marsdenia R.Br. species.

FIG. 2. ─ Marsdenia kaalaensis Meve, Gâteblé & Liede, sp. nov.: A, flowering stem; B, flower in top view; C, gynostegium with corona in lateral view; D, isolated style-head with still one pollinarium attached; E, pollinarium. Drawings: U. Meve from Pillon et al. 213, Fig. 2A drawn after a photograph taken by J. Munzinger. Scale bars: A, 5 mm; B, 2 mm; C-E, 0.2 mm.