Solanum semisucculentum D. McClelland, 2020

McClelland, Donald H. R., Nee, Michael & Knapp, Sandra, 2020, New names and status for Pacific spiny species of Solanum (Solanaceae, subgenus Leptostemonum Bitter; the Leptostemonum Clade), PhytoKeys 145, pp. 1-36 : 1

Solanum semisucculentum D. McClelland sp. nov. Figure 11

Diagnosis.

Like Solanum artense Montroux, but differing in its high elevation serpentine substrate habitat, very fleshy, semi-succulent stems and leaves, glabrous petioles and larger berries.

Type.

New Caledonia. Nord: Tiébaghi Massif, ca. 12 air-km northwest of Koumac, 8 Nov 1980 (fl, fr), G. McPherson 3303 (holotype: NOU [acc. #017344]; isotypes: MO [acc. #2924404, barcode MO-2282964], NSW [acc. #594228], P [P00301276], PTBG [acc. #032935]).

Description.

Shrub 1.5 m, the internodes to 4.5 m long, unarmed. Stems glabrous or with occasional yellow-ferruginous, sessile porrect-stellate trichomes, the rays 7-11, 0.05-0.15 mm long, the midpoint more or less equal to the rays, flexed to lie parallel to the stem, the stellate trichomes soon deciduous; new growth sparsely pubescent with sessile porrect-stellate trichomes and minute glandular hairs to 0.7 mm long; bark of older stems grey, the young stems bright purple. Sympodial units difoliate, the leaves not geminate. Leaves simple; blades 2.3-11.2 cm long, 1.0-3.4 cm wide, 2.3-3.6 times as long as wide, lanceolate to elliptic, fleshy to semisucculent, concolorous; adaxial surfaces glabrous or with a few scattered sessile porrect-stellate trichomes, if present these with 8-10 rays 0.1-0.15 mm long, the midpoint more or less equal to the rays; abaxial surfaces glabrous; principal veins 6-8(-9) pairs, the midrib raised abaxially and adaxially, the lateral veins weakly or strongly brochidodromous, raised abaxially, distinct adaxially; base rounded, cuneate, or short-attenuate, sometimes oblique; margins entire; apex acute to acuminate; petiole 0.6-3.0 cm long, 0.6-0.9 mm in diameter, glabrous or sparsely pubescent on the adaxial surface, channeled above. Inflorescence to 3.8 cm long, appearing lateral, extra-axillary, emerging from the upper 1/3 of the internode, unbranched, with up to 23 flowers, nearly glabrous, with occasional sessile porrect-stellate trichomes and minute glandular papillae; peduncle 1.0-1.4 cm long, 0.4-0.6 mm in diameter; pedicels 0.9-1.2 cm long, 0.2-0.4 mm in diameter at the base, 0.6-0.8 mm in diameter below the calyx, straight, bent approximately 90° below the calyx, gradually increasing in diameter in the distal 1/3-1/2, glabrous, articulated at the base; pedicel scars widely and evenly spaced 5-8 mm apart. Buds ovate, the calyx more or less glabrous to sparsely stellate-pubescent, the corolla densely stellate-pubescent where exposed abaxially, strongly exserted from the calyx before anthesis. Flowers 5(-6)-merous, heterostylous and the plants weakly andromonoecious. Calyx 1.3-5.3 mm long, appearing nearly truncate with apiculate to caudate lobe tips, the tube 0.5-1.1 mm long, the sinuses translucent when dry, the lobes 0.7-4.2 mm long, long-caudate, glabrous adaxially, sparsely pubescent abaxially, splitting in the sinuses during fruit development and then the lobes deltate. Corolla 1.2-2.5 cm in diameter, stellate, white, the interpetalar tissue well developed, the lobes 5.5-8.9 mm long, 5.4-6.8 mm wide, deltate, spreading at anthesis, adaxially glabrous at the base becoming densely stellate pubescent towards the apex, abaxially moderately to densely pubescent. Stamens equal; filament tube minute; free portion of the filaments 0.6-1.0 mm long, glabrous; anthers 4.2-6.2 mm long, 1.3-1.7 mm wide, markedly tapering, straight, yellow, more or less spreading, poricidal at the tips, the pores directed distally, extending around the edge of the apex. Ovary ca. 1.0 mm in diameter, globose, densely stellate-pubescent at the very apex only; style of long-styled flowers 7.7-8.3 mm long, ca. 0.3 mm in diameter, exserted from the anther cone, filiform, straight, moderately to densely pubescent on the basal 1/2-2/3 portion, the style of short-styled flowers 1.0-1.3 mm long, ca. 0.2 mm in diameter, included within the anther cone; stigma 0.4-0.6 mm in diameter, capitate, green in live plants. Fruit a globose or slightly elongate juicy berry, 0.8-1.3 cm in diameter, when immature evenly green, red to orange when mature, glabrous, the pericarp thin, glossy, opaque; fruiting calyx lobes 1.8-2.8 mm long, 0.9-3.5 mm wide, glabrous, appressed to the berry surface or reflexed; fruiting pedicels 1.5-2.4 cm long, 0.6-1.1 mm in diameter at the base, 1.6-2.9 mm in diameter below the calyx, straight or arching, gradually increasing in diameter in the distal 1/2-2/3, glabrous. Seeds 20-30(-40) per berry, ca. 2.2 mm long, 2.3-2.8 mm wide, flattened-orbicular and notched at the point of attachment, red-brown or tan when dry, the surface minutely pitted (alveolate) under a smooth, translucent seed coat, the walls of testal cells straight or slightly sinuate towards the seed center. Chromosome number not known.

Distribution and ecology

(Figure 7 ). Solanum semisucculentum is endemic to New Caledonia and is restricted to the ultramafic mountains of the western side of the Grande Terre. It is found in the North Province from (50-)100 to 700(-1,200) m elevation. This species is a serpentine endemic and grows in an open shrubby habitat (maquis) on soils which are fast draining and the semisucculent leaves of this species are possibly an adaptation for these harsh conditions.

Phenology.

Flowering and fruiting year round.

Etymology.

The specific epithet indicates the texture of the leaves and stems. This texture is best described as fleshy to semisucculent and is unusual in Solanum .

Preliminary conservation assessment

( IUCN 2019). EOO = 814 km2 [EN -Endangered]; AOO = 60 km2 [EN -Endangered]. Solanum semisucculentum is found in a number of localities in northern New Caledonia, all of which are in montane serpentine soil areas now highly disturbed by mining activities. We preliminarily assign an assessment of EN (B1a,b) due to its fragmented distribution and threats to its montane habitat from mining activities.

Discussion.

Heine (1976) treated specimens here recognized as S. semisucculentum in his concept of S. styraciflorum . The type of S. styraciflorum was probably destroyed at B during the Second World War, and no duplicates have been traced; specimens matching the protologue of S. styraciflorum exist (see www.solanaceasource.org) and McClelland (2012) treats S. styraciflorum as a synonym of S. artense Montroux. Solanum artense is sparsely to densely pubescent on the stems, along the midvein of the leaves adaxially, and sometimes the inflorescence; its leaves are chartaceous and typically have a greater leaf length to width ratio than S. semisucculentum . Specimens of S. semisucculentum differ from the protologue of S. styraciflorum in petiole pubescence (glabrous or very sparsely pubescent versus densely stellate-subvillose), berry size (7.5-12.5 mm diameter versus ca. 6.0 mm) and elevational range (300-500 m versus 50 m). Solanum artense (incl. plants matching the protologue of S. styraciflorum ) is found below 250 m on calcareous soils while S. semisucculentum is typically found at higher elevations, such as the plateau of the Dôme de Tiébaghi, at 300-500 m on lateritic soils.

Perhaps the most remarkable feature of S. semisucculentum is its very fleshy, semisucculent leaves. Many species of Solanum wilt shortly after collecting; S. semisucculentum , however, appears well adapted for water deprivation. With no difficulty, a specimen was kept alive after collecting it with a few roots but no soil and carrying it for a couple hours on a warm tropical afternoon (DHRM, pers. obs.). After a couple of days this specimen opened a flower which had been in bud when it was collected. Solanum semisucculentum has vividly purple stems which are quite striking in living material, but dry black on herbarium specimens. This coloration may provide a certain amount of protection of the high levels of solar radiation this species receives in its open maquis habitat.

Specimens examined.

New Caledonia. Nord: Dôme de Tiébaghi, 22 Jan 1976 (fl, fr), Blanchon 1444 (NOU, P); Mine Oubliée [near Pic Poya], 650 m, 7 Jan 1962 (fl, fr), Catala-Stucki 160 (G); Tiébaghi, 24 Sep 1961 (fl, fr), Denizot s.n. (P); Dôme de Tiébaghi, 8 Nov 1980 (fl), Hoff 2975 (NOU); Mt. Ninga, 1000 m, 15 Oct 1975 (fr), Jaffré 1415 (NOU, P [date 2 May 1976]); Dôme de Tiébaghi, 350 m, 15 Nov 1975, Jaffré 1415bis (P); Plateau de la Tiébaghi, 500 m, 15 Nov 1976 (fl, fr), Jaffré 1824 (NOU, P); Massif Boulinda, secteur Col Nekoro, 27 Jul 1972 (fl), Jaffré 2183 (NOU); Massif de Boulinda, above river Ouaha, east of Muéo, 100-200 m, 21.20 S, 165.05 E, 12 Dec 1973 (fl), Jaffré 19234 (NOU, P); Dôme de Tiébaghi, Pente Sud-Ouest du Dôme de Tiébaghi, 300-500 m, 9 May 1966 (fl), MacKee 14921 (K, P); pente nord du Mt. Kaala, 400-700 m, 9 Jul 1966 (fl, fr), MacKee 15272 (A, K, L, NOU, P); pente Nord du Mont Kaala, 700 m, 25 Dec 1966 (fl, fr), MacKee 16152 (K, L, NOU, NY); Haute Népoui, Oué Péoué, contrefort sud du Kopéto, 500 m, 8 Jul 1970 (fl), MacKee 22193 (P); Mt. Boulinda, 1200 m, 1 Jun 1972 (fl, fr), McKee 25571 (P); Dôme de Tiébaghi, 400 m, 30 Nov 1972 (fl, fr), MacKee 25953 (K, L, P); Nekoro, 200 m, 21 May 1977 (fr), MacKee 33195 (NOU, P); Dôme de Tiébaghi, Plateau central, 550 m, 8 Jul 1978 (fl, fr), MacKee 35432 (L, NOU, P); Koumac, Chagrin, 300 m, 8 Jan 1983 (fr), MacKee 41156 (P); Dôme de Tiébaghi, on the plateau south of the old town, 590 m, 15 Jul 2009 (fl, fr), McClelland & Nee 554 (MO, NOU, NY, P); Tiébaghi Massif, north of Koumac, 550 m, 20 Dec 1983 (fl, fr), McPherson 6169 (MO, NOU, PTBG); Boulinda, base, 23 Jan 2008 (fl, fr), Munzinger et al. 4959 (NOU); Tiébaghi, sur le plateau, côté Est, 14 Apr 2014 (fl, fr), Munzinger et al. 7575 (NOU); Dôme de la Tiébaghi, 400-600 m, 25 Jul 2007 (fl, fr) Pillon et al. 775 (NOU); pentes du Dôme de Tiébaghi, 13 Jun 1974 (fl, fr), Sévenet 685 (NOU); route minière d’accès au Bulinda [Boulinda], 20 Feb 1978 (fl, fr), Suprin 254 (NOU); Mt. Boulinda, 550 m, 26 Apr 1965 (fr), Veillon 129 (NOU, P); Dôme de Tiébaghi, plateau, ca. 550 m, 17 Aug 1965 (fl), Veillon 361 (NOU); Mt. Boulinda, ca. 400 m, 26 Jul 1967 (fl), Veillon 1268 (K, NOU, P); Dôme de Tiébaghi, ca. 550 m, 25 Nov 1967 (fl, fr), Veillon 1457 (NOU, P); pentes ouest du Dôme de Tiébaghi, ca. 500 m, 27 Oct 1943 (fl, fr), Virot 1274 (A, NOU, P).

Figures

Figure 7. Distribution of Solanum memoayoanum and S. semisucculentum.

Figure 11. Solanum semisucculentum D. McClelland (isotype McPherson 3303, MO [acc. 2924404, barcode MO- 2282964]). Reproduced with permission.