Solanum michaelis Saerkinen & S.Knapp, PhytoKeys 74: 22. 2016.

Knapp, Sandra, Saerkinen, Tiina & Barboza, Gloria E., 2023, A revision of the South American species of the Morelloid clade (Solanum L., Solanaceae), PhytoKeys 231, pp. 1-342 : 1

32. Solanum michaelis Saerkinen & S.Knapp, PhytoKeys 74: 22. 2016.

Figs 98 , 99

Type.

Bolivia. Tarija: Prov. Gran Chaco, 44.5 km (by rd) W from upper bridge over Rio Pilcomayo and 17.7 NE of Palos Blancos, on rd from Villa Montes to Palos Blancos , 815 m, 21 Mar 2007, M. Nee & R. Flores S. 54821 (holotype: LPB; isotypes: BM [BM001211859], CORD [CORD00094450], MO [MO-2113149, acc. # 6073914], NY [00853628], SI [075094, acc. # 112169], US [02836465, acc. # 3595978], UT [acc. # 126715]; [records indicate that additional duplicates were sent to CAS, G, MEXU, NSW, USZ, WIS]).

Description.

Decumbent to erect subwoody herb to 1 m high, spreading to up to 2 m in diameter. Stems 3-4 mm in diameter at base, spreading or erect, terete, straw-coloured, glabrescent; new growth densely glandular-papillate and pubescent with a mixture of patent, simple, uniseriate eglandular and glandular trichomes, the trichomes of several lengths, 1-celled to 17-celled, 0.2-2 mm long, translucent, if glandular then with a terminal gland (this often breaking off). Sympodial units difoliate, not geminate. Leaves simple and shallowly lobed, the blades (2.4-)4-7.6 cm long, (1.4-)2.3-3(-4) cm wide, ovate, widest in the lower third, membranous, concolorous or slightly discolorous; adaxial surface moderately pubescent with both eglandular and glandular hairs along lamina and veins; abaxial surface more densely pubescent along veins; major veins 3-5 pairs; base truncate to rounded; margins entire to shallowly and unevenly lobed (mostly near the base); apex acute; petiole (0.7-)1.5-2 cm long, pubescent with spreading eglandular and glandular hairs like those on the stem. Inflorescences internodal or opposite the leaves, unbranched, 2.5-3.5 cm long, with (6-)7-10(-12) flowers, pubescent with both eglandular and glandular trichomes like those on stem; peduncle 1.4-3.3 cm long; pedicels spaced 0-1 mm apart, 6-10 mm long, ca. 0.2 mm in diameter at base and apex, straight and spreading at anthesis, articulated at the base. Buds ellipsoid, white or purple-tinged, densely pubescent with spreading, multicellular hairs (see description of calyx), the corolla not strongly exserted from the calyx, exceeding the calyx lobes by less than 1/2 of their lengths before anthesis. Flowers 5-merous, cosexual (hermaphroditic). Calyx tube 0.8-1.3 mm long, the lobes 1.4-3.7 mm long, 0.6-1 mm wide, triangular with long-acuminate apices, densely pubescent with both eglandular and glandular trichomes, the eglandular trichomes 1.5-3.5 mm long. Corolla 0.7-1.3 cm in diameter, white with a green-black basal central star, stellate, lobed halfway to the base, the lobes 2.5-3.2 mm long, 1.5-2.5 mm wide, reflexed at anthesis, later spreading, sparsely pubescent abaxially with multicellular simple spreading eglandular uniseriate trichomes to 0.5 mm long, densely papillate on the tips and margins. Stamens equal; filament tube 0.1-0.25 mm long; free portion of the filaments 0.2-0.3 mm long, adaxially pubescent with tangled eglandular simple uniseriate trichomes; anthers 2.5-3.2 mm long, 0.9-1.1 mm wide, ellipsoid, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary subglobose, glabrous; style 4-5 mm long, straight, exserted beyond the anther cone, densely pubescent with 4-celled simple uniseriate trichomes in the basal 1/2 or 3/5 where included in the anther cone; stigma capitate, the surface minutely papillate. Fruit a subglobose berry, slightly flattened, 0.5-1.2 cm in diameter, green and mottled with white vein-like reticulations (black when ripe fide Fuentes & Navarro 2607), the pericarp thin, shiny, translucent, glabrous; fruiting pedicels 1.6-2 cm long, ca. 0.5 mm in diameter at the base, ca. 1 mm in diameter at the apex, spaced 1-2 mm apart, strongly deflexed, not persistent, leaving raised pedicel scars to 0.1 mm high; fruiting calyx tube 2-2.5 mm long, the lobes 5-8 mm long and 3-3.5 mm wide, spreading to reflexed. Seeds 15-25 per berry, 1.7-2 mm long, 1.1-1.5 mm wide, teardrop shaped and somewhat flattened, pale brown, the surface minutely pitted, the hilum positioned subapically, the testal cells pentagonal in outline. Stone cells absent. Chromosome number: not known.

Distribution

(Fig. 100 ). Solanum michaelis occurs in Bolivia (Depts. Chuquisaca, Santa Cruz, Tarija), northern Argentina (Prov. Salta) and Paraguay (Dept. Presidente Hayes).

Ecology and habitat.

Solanum michaelis grows in dry Chaco vegetation and in lower inter-Andean valleys, along slopes in sandy soils in mostly unshaded dry creek beds on bare soil, often in areas that have been burned, or in more humid Chaco vegetation at the edge of “palmares” (stands of Copernicia alba Morong, Arecaceae ), between 300 and 900 m elevation.

Common names and uses.

None recorded.

Preliminary conservation status

( IUCN 2022). Least Concern [LC]. EOO = 1,008,132 km2 [LC]; AOO = 468 km2 [EN]. Särkinen and Knapp (2016) assigned a preliminary threat status of Endangered to S. michaelis . Although many more collections of this species have been found since its description, collection densities in the Chaco remain low, and S. michaelis is likely to be highly vulnerable to grazing pressure and changes in rainfall patterns due to its ephemeral ecology as an annual plant and its threatened habitat. The Chaco woodlands are highly threatened by land use change due to agricultural expansion and logging ( Huang et al. 2009). Two populations are known to occur within the protected area network in Bolivia (e.g., Parque Nacional de Gran Chaco Kaa-lya along the border with Paraguay, and Parque Nacional de Serranía del Aguaragüe).

Discussion.

Solanum michaelis differs from the co-occurring and morphologically similar glandular-pubescent S. sarrachoides and S. physalifolium in having larger anthers (2.5-3.2 mm long); both S. sarrachoides and S. physalifolium have anthers less than 2.2 mm long. Solanum physalifolium has similar shiny, green-mottled berries, but occurs at higher elevations (1,400 to 2,900 m) in ‘yungas’ or moist forest vegetation and has broadly ovate calyx lobes that partially enclose the fruit at maturity. Solanum physalidicalyx has similarly sized anthers, but a longer calyx tube (ca. 1.5-2 mm in flower and to ca. 5 mm or more in fruit) which is inflated and fully encloses the berry both during development and at fruit maturity (see Knapp et al. 2020). Solanum michaelis has similarly long calyx lobes but a shorter calyx tube in both flower (0.8-1.3 mm) and fruit (2-2.5 mm) that does not enclose the fruit and appears to sometimes have reflexed calyx lobes at fruit maturity (e.g., Fuentes & Navarro 2607). The more widely distributed S. tweedieanum has much longer anthers (4-5 mm long), whitish green mature berries and the calyx tightly encloses the berry during development, but the berry can be somewhat exposed at maturity.

Figures

Figure 98. Solanum michaelis A habit B inflorescence C maturing fruits (A-C Nee & Flores 54821 [BM 001211859]). Reproduced with permission of the Trustees of the Natural History Museum.

Figure 99. Solanum michaelis A fruiting stem B inflorescence with details of mixed glandular and eglandular pubescence C flower at anthesis D maturing fruit (A-D Nee & Flores 54821). Photos M. Nee. Previously published in Saerkinen and Knapp (2016: 23).

Figure 100. Distribution map of Solanum michaelis.