Solanum humblotii Dammer, Bot. Jahrb. Syst. 38: 184. 1906.

Knapp, Sandra & Vorontsova, Maria S., 2016, A revision of the " African Non-Spiny " Clade of Solanum L. (Solanum sections Afrosolanum Bitter, Benderianum Bitter, Lemurisolanum Bitter, Lyciosolanum Bitter, Macronesiotes Bitter, and Quadrangulare Bitter: Solanaceae), PhytoKeys 66, pp. 1-142 : 36-40

Solanum humblotii Dammer, Bot. Jahrb. Syst. 38: 184. 1906. Figure 9

Type.

Madagascar. Sin. loc., L. Humblot 509 (type material presumably destroyed at B; lectotype, designated here: P [P00349085]; isolectotypes: K [K000414188], P [P00349086, P00349087, P00349088], W [W-1889-0053791]) .

Description.

Liana in the subcanopy or canopy or a scandent shrub, to 3 m tall or perhaps larger. Stems flexuous, ribbed, glabrous or pubescent with minute uniseriate dendritic trichomes ca. 0.1 mm long or less, glabrescent; new growth finely and minutely pubescent with dendritic trichomes <0.1 mm long; bark of older stems longitudinally ridged, often exfoliating or flaking, pale grey to almost white. Sympodial units plurifoliate, the leaves not geminate, evenly distributed along branches. Leaves simple, 5.5-7.5 cm long, 2.5-3 cm wide, elliptic, thickly chartaceous, discolorous, glabrous and smooth on both surfaces except for minute dendritic and simple trichomes along the midrib; major veins 3-6 pairs, spreading at 60°-90° to the midvein, not prominent and the finer venation not visible; base equal or oblique, cuneate to truncate; margins entire, glabrous or with occasional minute dendritic trichomes; apex short-acuminate; petiole 0.6-1 cm long, canaliculate and minutely dendritic-pubescent adaxially. Inflorescences terminal or apparently lateral on long slender main branches, 0-2 cm long, unbranched, with 1-2(4) flowers, glabrous or with a few minute dendritic trichomes; peduncle absent or up to 8 mm long; pedicels 1.8-4.5 cm long, apically dilated, ridged when dry, articulated 0-2 mm from base, sparsely pubescent with trichomes like those on the stem with the branches to 0.15 mm long. Buds ellipsoid, the corolla soon exserted from the calyx tube. Flowers 5-merous, apparently all perfect. Calyx tube ca. 3 mm long, cup-shaped, the lobes 2-4 mm long, 1.5-2 mm wide at base, narrowly triangular to deltate, acute to long-acuminate at the tips, unevenly tearing for up to ca. 2 mm at the sinuses, often tinged purple in live plants (e.g., Tosh et al. 100) evenly and sparsely pubescent with minute dendritic trichomes 0.1-0.2 mm long. Corolla 2-2.5 cm in diameter, violet to deep purple with a white centre (fide Schatz & Villiers 1820), stellate, lobed almost to base, the 8-10 mm long, 4-5 mm wide, ovate to linear, finely dendritic-pubescent abaxially, the trichomes longer and denser at the margins and tips. Stamens equal; filament tube 0.5-1 mm long; free portion of the filaments ca. 1 mm long; anthers ca. 3.5 mm long, ca. 1.5 mm wide, apparently free but close together, ellipsoid, smooth abaxially, poricidal at the tips, the pores clearly delineated and not lengthening with age. Ovary conical, glabrous; style 9-10 mm long, protruding 3-3.5 mm above the anthers, straight, glabrous; stigma clavate or capitate, minutely papillose. Fruit a globose berry, green when immature; fruiting pedicels not markedly elongating or woody. Seeds not known from mature fruit.

Distribution

(Figure 10 ). Endemic to northern Madagascar in the province of Toamasina and on the island of Nosé Mangaby.

Ecology and habitat.

Littoral forests on white sand and inland eastern rainforests; sea level to 700 m elevation.

Common names and uses.

None recorded.

Preliminary conservation status

( IUCN 2014). Near Threatened (NT). EOO 20,941 km2 (NT), AOO 40 km2 (EN). Solanum humblotii is confined to wet forests (see below), and is rarely collected. Given the decreasing extent of wet forests in Madagascar, this species is certainly of conservation concern, but it does occur in or near some forestry reserves, so may have some degree of protection.

Discussion.

Solanum humblotii is a forest liana with minute dendritic pubescence, triangular to long-triangular calyx lobes and thickly chartaceous discolorous leaves with an apiculate tip. The name Solanum humblotii has been mistakenly applied Solanum truncicola following the synonymy established by D’Arcy and Rakotozafy (1994), and to Solanum madagascariense though misidentification.

The vegetative morphology of Solanum humblotii is very similar to some populations of the widespread Solanum madagascariense . The two species can be distinguished easily on inflorescence size and calyx morphology. The inflorescence of Solanum humblotii has only 2-3 (exceptionally 4) flowers on long filiform pedicels and is never branched, while that of Solanum madagascariense is many times branched with many flowers except on some aberrant specimens; calyx lobes are 3-4.5 mm long in Solanum humblotii , and up to 1 mm long in Solanum madagascariense .

Specimens here recognised as Solanum truncicola were treated as Solanum humblotii by D’Arcy and Rakotozafy (1994), where the two were treated as synonyms. The two species are similar, and prior to our study Solanum humblotii was only known from the type collection. Further collecting in the wet forests of northern Madagascar has resulted in more specimens with which to assess the status of these two taxa (see also discussion under Solanum truncicola ).

Solanum humblotii differs from Solanum truncicola by its petioles that are 6-10 mm (versus 1-5 mm) long, acuminate (versus acute) leaves, pubescent (versus glabrous) young stems, and inflorescences with a peduncle up to 5 mm long (versus no peduncle). The calyx of Solanum humblotii is fused in bud (Fig. 9 ); the tube is longer than the lobes and tears for up to 2 mm at anthesis with corolla expansion. The resulting calyx lobes are 3-4.5 mm long, triangular to narrowly triangular and acuminate, chartaceous, and sparsely covered in fine dendritic (almost scurfy) pubescence. This calyx morphology is similar to that of Solanum imamense , Solanum betroka and Solanum sambiranense . The calyx of Solanum truncicola is unlike that of any other Madagascar Solanum . It is dissected almost to the base in bud and does not tear by more than 1 mm at anthesis; the calyx lobes are linear to narrowly ovate or obovate, membranous, and usually glabrous.

Solanum humblotii is restricted to a small area of wet forest in the eastern ecoregion of Madagascar ( Humbert 1955; Faramalala 1988, 1995), a habitat like that of the related wet forest climbing species Solanum madagascariense and Solanum trichopetiolatum . It is sympatric with the morphologically similar Solanum madagascariense and occurs considerably further south of Solanum trichopetiolatum ; the distribution range of the epiphyte Solanum truncicola lies directly to the south of Solanum humblotii with some overlap in distribution ranges around the Moramanga area.The locality of the type collection within Madagascar is not known, but is likely to be from the region where all other specimens of Solanum humblotii have been collected. Dammer (1906) describes it as a shrub but the type specimens contain no such information; modern collections record a variety of growth forms (shrub, liana and epiphyte) in both primary and secondary habitats.

Udo Dammer worked in Berlin and it is likely he used specimens held there to describe Solanum humblotii but these are no longer extant. Of the four duplicates of Humblot 509 in the herbarium in Paris, we have chosen P00349085 as the lectotype due to its numerous flowers and excellent condition.

Selected specimens examined.

Madagascar. Toamasina: Parc National de Masoala, sur la route d’Ambanizana à Analambolo (25 km N de la ville d’Ambanizana), ca. 6 km NE d’Ambanizana, Fiv. Maroantsetra , 24 Jan 1996, Aridy et al. 77 (MO, NY); Zahamena, réserve naturelle N°3, 23 Mar 1941, Decary 16757 (P); Moramanga, Fanovana, forêt orientale, 10 Jul 1942, Decary 18118 (P); Tampolo Forest Station , ca. 10 km N of Fenerive, 23 Jan 1986, Dorr et al. 4637 (K, MO, P, TAN, WAG); Tampolo STF, District Fénérive-Est, Canton Ampasina, Tampolo, station forestière de Tampolo, 2 Jul 2001, Ludovic et al. 110 (G, MO, P); Antandrokonely, lac Alaotra, Jun 1957, Peltier & Peltier 980 (P); forêt littorale classée de Tampolo, près du village Tanambao-Tampolo, Fenoarivo-Est, 5 Apr 1997, Ralimanana et al. 96 (MO, TAN); Maroantsetra, Nosy Mangabé, a 520 ha island 5 km from Maroantsetra in the bay of Antongil , 2 Dec 1987, Schatz & Villiers 1820 (K, MO, P, TAN, WAG); Tampola , 3 km N of Tampola Forestry Reserve, 14 Jan 2006, Tosh et al. 100 (BR, TAN) .

Figures

Figure 9. Solanum humblotii Dammer. A Flowering branch B Flower bud C Open flower D Fruiting branch E Berry F Simple trichome G Dendritic trichome. (based on: A-C Ralisamana et al. 96; D-G Tosh et al. 100). Scale bar: A, D = 3 cm; B, C = 1 cm; E = 1.5 cm; F, G = 0.2 mm. Drawn by Lucy T. Smith.

Figure 10. Distribution of Solanum humblotii Dammer.