Solanum homalospermum Chiarini, Brittonia 56: 284. 2004.

Knapp, Sandra, Sagona, Eva, Carbonell, Anna K. Z. & Chiarini, Franco, 2017, A revision of the Solanum elaeagnifolium clade (Elaeagnifolium clade; subgenus Leptostemonum, Solanaceae), PhytoKeys 84, pp. 1-104 : 26

3. Solanum homalospermum Chiarini, Brittonia 56: 284. 2004. Figures 2B , 9

Type.

Argentina. Córdoba: Dpto. Sobremonte, a 6 km de San Francisco de Chanar , a orilla de ruta rumbo a Lucio V. Mansilla, 29°46'34"S, 63°59'59"W, 29 Nov 2001, F. Chiarini, G. Barboza & M. Matesevach 505 (holotype: CORD [CORD00004226]; isotype: NY [NY00804056]) .

Description.

Erect rhizomatous shrub, 0.3-0.5 m tall. Stems sparsely armed or more commonly unarmed; young stems densely pubescent, the trichomes stellate, porrect, yellowish golden, sessile and short-stalked, the rays 6-8, ca. 1 mm long, the midpoints up to 1 mm long, equal in length to the rays; prickles if present 5-6 mm long, straight, slightly wider at the base, pale yellowish brown; bark of older stems smooth, brown or yellowish brown from persistent pubescence. Sympodial units difoliate or trifoliate, not markedly geminate. Leaves simple, 3-8 cm long, 1-3.1 cm wide, elliptic to narrowly elliptic, 4-5 times longer than wide, mostly concolorous, drying yellowish green to green; adaxial surfaces densely pubescent with translucent, mostly sessile porrect, stellate trichomes, the rays 8-14, 0.05-0.2(0.3) mm long, straight, the midpoint up to 0.1 mm, often reduced; abaxial surfaces densely pubescent with stalked porrect, stellate trichomes, the stalks to 0.5 mm long, the rays 8-10, 0.4-0.6 mm long, the midpoint shorter; principal veins 4-8 pairs, impressed adaxially, flat abaxially, spreading at ca. 45° to the midvein, the tertiary venation mostly not visible due to the dense pubescence; base acute; margins entire, rarely very shallowly lobed, the lobes 2-3 on each side, the sinus extending only 1/8 or less of the distance to the midvein, rounded; apex obtuse, rarely rounded; petiole 0.5-1.5 cm long, densely stellate-pubescent like the young stem, prickly, the prickles ca. 2 mm long, acicular. Inflorescences terminal or lateral, to 5 cm long, with up to 10 flowers, unbranched; peduncle less than 0.2 cm long, the lowest flower arising from very near the main axis; pedicels ca. 2 cm long, ca. 2 mm in diameter, robust, articulated near the base, densely stellate-pubescent like the leaf blades, the basal flower with the pedicel prickly, the prickles 2-3 mm long, orange-yellow; pedicel scars prominent, spaced 0.5-1.5 cm apart, space between the basal flower and the next much longer than that between the more distal staminate flowers. Buds ellipsoid, the calyx ca. 1/2 of the corolla length prior to anthesis. Flowers strongly heteromorphic and the plants andromonoecious, only the basal flower perfect and long-styled, the rest functionally staminate and short-styled. Calyx conical or cup-shaped, the tube 3-5 mm long, the lobes (3)6-8 mm long, 3-4 mm wide at base, lanceolate or long-deltate with acuminate apices, densely stellate-pubescent abaxially like the leaf blades, prickly in basal hermaphroditic flowers. Corolla 3-4 cm in diameter, white, drying yellowish-light brown, stellate, lobed for ca. 1/2 of the length, the lobes 0.8-1.5 cm long, ca. 1.2 cm wide, broadly deltate, densely stellate-pubescent abaxially. Stamens unequal, with the 2 adaxial anthers shorter than the 3 abaxial anthers; filament tube 1-1.5 mm, free portion of the filaments 3-5 mm; anthers 8-12 mm long, free, slightly unequal, poricidal at the tips, the pores about the same diameter as the anther apices, clearly delineated, the anther surface smooth to finely papillose. Ovary globose, minutely puberulent with simple glandular trichomes and some stellate trichomes; style of hermaphroditic flowers ca. 10 mm long, glabrous or minutely puberulent in the lower half; stigma capitate, papillose. Fruit a globose berry, 1 per infructescence, 1.2-3.5 cm in diameter when dry, the pericarp thin, smooth, glabrous, greyish brown and chartaceous when mature, when immature light green with dark stripes or marbled pattern, drying dark brown; fruiting pedicels 3-4 cm long, ca. 2 mm in diameter at base, 3-4 mm at apex, woody, strongly deflexed, sparsely armed with straight yellowish red prickles or unarmed, channelled in dry specimens; fruiting calyx accrescent, to 1.5 cm long, the lobes covering 2/3 or the entirety of the mature fruit, sparsely prickly. Seeds ca 10-30 per berry, 5-6 mm long, ca. 2.5 mm wide, flattened, reniform-rounded, brown, the surface minutely pitted and somewhat warty. Chromosome number: n=ca. 24 ( Chiarini et al. in press; Chiarini 505).

Distribution

(Figure 8 ). Solanum homalospermum is endemic to north central Argentina in the Provinces of Córdoba and adjacent Catamarca at ca. 700 m elevation.

Ecology and habitat.

Solanum homalospermum grows in open areas in the dry Chaco forest region; the vegetation at the type locality is a highly disturbed palm ( Trithrinax Mart., Arecaceae ) woodland-grassland ( Zak and Cabido 2002). This species has a complex root system that facilitates vegetative reproduction and spread like other members of the Elaeagnifolium clade.

Common names and uses.

None known.

Preliminary conservation status

( IUCN 2016). Endangered/Critically Endangered (EN/CR). EOO = 273 km2 (EN- Endangered); AOO = 12 km2 (EN - Endangered). Solanum homalospermum might best be considered CR (Critically Endangered) because the EOO and AOO measures are at the low end of the EN scale ( IUCN 2016). It is known only known from two localities (see Specimens examined) and despite repeated recent searches by F. Chiarini and colleagues, has not been found since its first description.

Discussion.

Solanum homalospermum is partially sympatric with S. elaeagnifolium and S. mortonii . It is similar to S. elaeagnifolium in its narrowly elliptic or lanceolate leaves, but can be distinguished from that species by its porrect-stellate, rather than lepidote, pubescence and strongly andromonoecious breeding system with a single hermaphroditic flower at the base of the inflorescence. It differs from S. mortonii in its lanceolate, concolorous leaves, porrect-stellate rather than multangulate pubescence, and in its strongly deflexed fruiting pedicel. Solanum homalospermum occurs at (usually) lower elevations and to the east of the main distribution of S. mortonii (see Figs 8 and 12 ).

Specimens examined.

ARGENTINA. Catamarca: La Paz , km 981, 4 Apr 1950, Brizuela 1164[a] (CORD) . Córdoba: Sobremonte, Sierra del Norte, ca. 6-7 km al oeste de la plaza de San Francisco de Chanar , rumbo a Lucio V. Mansilla, 20 Jan 1987, Hunziker & Subils 24942 (CORD) .

Figures

Figure 2. Flowers of members of the Elaeagnifolium clade. A Solanum elaeagnifolium, with divergent anthers of approximately equal size and shape (Argentina, Mendoza, Knapp et al. 10470) B Solanum homalospermum (Argentina, Catamarca, Chiarini et al. 505) C Solanum hindsianum (cultivated in Arizona) D Solanum houstonii, hermaphroditic flower and strongly curved buds (Mexico, Yucatan, Pena-Chocarro et al. 407) E Solanum houstonii, staminate flower (Mexico, Queretaro, Ochoterena et al. 976) F Solanum mortonii (cultivated in Cordoba; from Barboza et al. 644). Photographs A, D, E by S. Knapp; B, F by F. Chiarini; C by Eugene Sturla.

Figure 8. Distribution of S. hindsianum and S. homalospermum.

Figure 9. Solanum homalospermum Chiarini A Whole plant B Stellate trichome from adaxial leaf surface, seen from the side C Stellate trichome from adaxial leaf surface, seen from above, D. Long-styled flower E Calyx F Spread corolla G Dorsal view of stamen H Ventral view of stamen I Gynoecium of long-styled flower J Gynoecium of short-styled flower, K. Fruit L Seed M Transverse section of seed. Drawn by Laura Ribulgo. All from Chiarini et al. 505 (CORD). Reproduced with permission from Flora Argentina (Chiarini 2013).

Figure 12. Distribution of S. houstonii and S. mortonii.