Solanum leptocaulon Van Heurck & Muell .Arg., Observ. Bot. 40. 1870.

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

28. Solanum leptocaulon Van Heurck & Muell.Arg., Observ. Bot. 40. 1870.

Figs 86 , 87

Solanum rheithrocharis Bitter, Repert. Spec. Nov. Regni Veg. 13: 91. 1914. Type: Bolivia. Cochabamba: "aplinen region oberhalb Incacorral", ca. 3,200 m, Jan 1908, T. Herzog 806 (lectotype, designated here: Z [Z-000229529]; isolectotype: L [L 0403634]).).

Solanum pongoense Rusby, Mem. New York Bot. Gard. 7: 348. 1927. Type. Bolivia. La Paz: Pongo de Quime, 5 Jul 1921, O.E. White 165 (holotype: NY [00172138]; isotype: US [00027754, acc. # 1185617]).

Type.

Bolivia. La Paz: Larecaja , "viciniis Yani, in scopulosis", Mar 1858, G. Mandon 404 (lectotype, designated here: G [G00359948 = F neg. 23126, two sheets]; isotypes BM [BM000778198], BR [BR0000005537884], F [v0073313F, acc. # 680216], G [G00370041], GH [00077702], K [K000585550], NY [00172062, 00022559, 00172063], P [P00336757], S [acc. # 04-2925]) .

Description.

Herbs or creeping subshrubs, often sprawling and rooting at the nodes to 0.5(1) m high; stems terete, sparsely pubescent with white eglandular simple uniseriate trichomes 0.5-0.75 mm long, these stiff and antrorse, 3-4-celled, the cells elongate; new growth sparsely to moderately pubescent with antrorse white simple uniseriate trichomes like those of the stems, or occasionally almost glabrous; bark of older stems pale grey or brown, glabrescent. Sympodial units plurifoliate, the leaves not geminate, but sometimes paired at the nodes. Leaves simple, the blades 0.9-5 cm long, 0.5-2 cm wide, narrowly elliptic to elliptic, widest at the middle or occasionally with some leaves widest in the lower third and somewhat hastate, membranous or slightly thick and fleshy, concolorous; adaxial surfaces evenly and sparsely to moderately pubescent with white eglandular simple 2-4-celled uniseriate trichomes 0.5-0.8(2) mm long, these stiff and antrorse; abaxially similarly but more sparsely pubescent with stiff antrorse trichomes, these densest along the veins, but also some on the lamina; principal veins 3-5 pairs, barely visible above except for the prominent somewhat keeled midrib, often drying yellowish brown below; base acute to somewhat acuminate; margins entire and minutely revolute, sometimes with two teeth ca. 1 mm long near the base; apex acute or somewhat rounded; petioles 0.2-1 cm long, pubescent like the stems. Inflorescences opposite the leaves or terminal, unbranched or rarely forked (on the same plant, e.g., Brooke 6038), 1-3 cm long, with 1-4(10) flowers clustered at the tips, almost glabrous to sparsely pubescent with white eglandular simple uniseriate trichomes 0.3-0.5 mm long, these stiff and antrorse; peduncle 0.8-2.5 cm long; pedicels 0.8-1 cm long, 0.4-0.5 mm in diameter at the base, 1-1.2 mm in diameter at the apex, filiform and spreading, sparsely pubescent with simple trichomes like the rest of the inflorescence, articulated at the base; pedicel scars closely spaced and clustered at the tips of the inflorescence axis or branches. Buds ellipsoid, the corolla strongly exserted from the calyx before anthesis. Flowers 5-merous, cosexual (hermaphroditic). Calyx tube 1.5-2 mm long, narrowly cup-shaped, the lobes 1.5-2 mm long, 1-1.2 mm wide, triangular, glabrous or with tiny simple uniseriate trichomes ca. 0.2 mm long, the sinuses transparent, drying white and scarious. Corolla 2-2.4 cm in diameter, 1-1.2 cm long, pale violet, campanulate, lobed ca. 1/4 of the way to the base, the lobes 2-4 mm long, 5-6 mm wide, slightly incurved, adaxially glabrous, abaxially densely puberulent with tiny white uniseriate trichomes ca. 0.2 mm long where exposed in bud especially along petal midveins, appearing less pubescent with flower age due to expansion, the interpetalar tissue glabrous. Stamens equal, completely hidden within the corolla tube; filament tube minute; free portion of the filaments 1-1.5 mm long, with tangled transparent simple uniseriate trichomes adaxially; anthers 2.5-3 mm long, ca. 1 mm wide, ellipsoid, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary conical, glabrous; style 5-7 mm long, straight, exserted beyond the anther cone, densely pubescent in the lower half, entirely within the corolla tube; stigma globose-capitate to somewhat clavate, the surface minutely papillate. Mature fruits and seeds not known. Chromosome number: not known.

Distribution

(Fig. 88 ). Solanum leptocaulon is known from the Andes of Bolivia (Depts. Cochabamba, La Paz, Santa Cruz) and from a single collection in southern Peru (Dept. Cusco).

Ecology and habitat.

Solanum leptocaulon grows in high elevation grasslands or cloud forest margins, usually above timberline or in open areas of puna or pre-puna vegetation, from 1,870 to 3,950 m elevation.

Common names and uses.

None recorded.

Preliminary conservation status

( IUCN 2022). Least Concern [LC]. EOO = 66,386 km2 [LC]; AOO = 120 km2 [EN]. The relatively wide distribution of S. leptocaulon does not suggest it is of immediate conservation concern, but pressure from mining and grazing in the high elevation grassy areas where it occurs may impact the species in the future. It occurs near protected areas in Bolivia (e.g., Parque Nacional Amboró, Parque Nacional Tunari and Parque Nacional Carrasco) but we have seen no collections from within the parks.

Discussion.

Solanum leptocaulon is a semi-prostrate, straggly shrub of high elevations mostly from northern Bolivia; Jardim 829 (Parque Nacional Tunari in Bolivia) is unusual in being recorded as a shrub 1 m high. It is similar to both S. albescens and S. dianthum , both also from the Bolivian Andes, and in the past specimens of these three taxa have been annotated as one or the other species somewhat chaotically. Solanum leptocaulon differs from S. albescens in its leaves with uniform short, stiff white pubescence (versus glabrous with longer curling trichomes confined to the stems and leaf margins), smaller corollas (1.1.2 cm long versus 1.5-1.8 cm long) and triangular calyx lobes (versus calyx lobes with somewhat fleshy expanded tips). Both species have campanulate flowers and anthers of more or less the same size, but the larger corollas of S. albescens make the anthers seem smaller.

Solanum dianthum is a shrub to 2 m high and often has geminate leaves, and like S. leptocaulon has even pubescence on stems and leaves. The most striking difference between S. leptocaulon and S. dianthum is the corolla shape; S. leptocaulon has campanulate corollas, while those of S. dianthum are stellate with distinct deltate lobes. The anthers of S. leptocaulon are shorter than those of S. dianthum (2.5-3 mm long versus 3.5-5 mm long). Fruits and seeds of S. leptocaulon are not known.

The protologue of S. leptocaulon ( van Heurck and Müller Argoviensis 1870) cites a single collection, Mandon 404 from two Herbaria "hb. Van Heurck et hb. DC.". We have selected the duplicate from the De Candolle Herbarium (that not used for the Prodromus and bearing a label to that effect) as the lectotype (G00359948), as it is the best preserved of the cited specimens and is annotated by J. Müller ( Müll.-Arg.). As is the case in the herbarium at Geneva, the specimen consists of two sheets, only the one without the barcode bears the original label (see Turland et al. 2018, Art. 8.3, Ex. 9).

Two collections were cited in the protologue of S. rheithrocharis ( Bitter 1914b), Kuntze s.n. from "herb. Berol." and Herzog 806 from "herb. Turic." [Z] ( Bitter 1914b). The specimen of Kuntze’s collection in Berlin was destroyed ( Zanoni 1980), the duplicate held in NY is not of good quality and is probably a specimen of S. dianthum . We thus select the other syntype, Herzog 806 at Z (Z-000229529) as the lectotype; it bears an annotation label in Bitter’s hand.

Rusby (1927) stated in his introduction to descriptions of plants of the Mulford Expedition to Bolivia that "all type specimens are to be found in the herbarium of The New York Botanical Garden", so even though a herbarium was not cited in the description of S. pongoense itself the specimen of White 165 in NY (00172138) is the holotype.

Figures

Figure 86. Solanum leptocaulon A flowering habit B flowering habit with larger leaves C fruiting habit D detail of adaxial leaf surface E detail of abaxial leaf surface F floral bud G dissected flower H maturing fruit (A, C-E Brooke 6038 B Ugent & Ugent 5066 F, G, H Steinbach 648). Illustration by R. Wise.

Figure 87. Solanum leptocaulon A habit B flowering branch C leaves D flower at full anthesis (A Mandon 404 [BM 000778198], reproduced with permission of the Trustees of the Natural History Museum B-D Nee et al. 55364). Photos of live plants by S. Stern.

Figure 88. Distribution map of Solanum leptocaulon.