Solanum dianthum Rusby, Bull. New York Bot. Gard. 4: 420. 1907.

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

14. Solanum dianthum Rusby, Bull. New York Bot. Gard. 4: 420. 1907.

Figs 44 , 45

Solanum hylobium Bitter, Repert. Spec. Nov. Regni Veg. 11: 223. 1912. Type. Bolivia. La Paz: Prov. Nor Yungas, Unduavi, Nov 1910, O. Buchtien 768 (no herbaria cited; lectotype, designated here: US [00027609, acc. # 1176007]; isolectotypes: CORD [CORD00013412], GH [00077682], GOET [GOET003539, GOET003540], NY [00172030], US [00027608, acc. # 175975; 00650471, acc. # 7073337]).

Type.

Bolivia. La Paz: Nor Yungas, Unduavi , Sep 1894, M. Bang 2492 (no herbaria cited; lectotype, designated here: NY [00139131], isolectotypes: F [v0073257F, acc. # 163985], GH [00077615], K [K000585512], MO [MO-503628, acc. # 3830685], NY [00139130], WIS [v0256186WIS]) .

Description.

Weak straggly shrubs or suffrutescent herbs, to 2 m high, often supported on other plants. Stems terete or slightly winged, occasionally with spinescent processes, moderately to densely pubescent with transparent or translucent eglandular simple, uniseriate 6-10-celled trichomes to 2 mm long, these spreading or somewhat appressed (longer, more spreading trichomes in populations from Unduavi, Bolivia); new growth densely pubescent with the same trichomes as those of the stems; bark of older stems yellowish brown, glabrescent. Sympodial units difoliate, the leaves geminate and usually paired at the nodes. Leaves simple, the blades 1.5-9 cm long, 0.8-4 cm wide, narrowly elliptic to elliptic (ovate in some plants from Unduavi populations), widest at the middle or in the lower half, membranous, concolorous, but some plants from Sud Yungas, Bolivia (e.g., Solomon 6043, 7297, 13691, 13854) dark purple beneath; adaxial surfaces sparsely and evenly pubescent with eglandular simple uniseriate trichomes ca. 1 mm long, these to 6-celled, appressed to the lamina and antrorse or somewhat more spreading; abaxial surfaces similarly pubescent, but the trichomes denser on the veins; principal veins 6-8 pairs, drying yellowish below; base acute (truncate or sightly cordate in Unduavi populations); margins entire, occasionally with a few irregular teeth to 3 mm long, 3 mm wide; apex acute to slightly elongate-acute; petioles (0.3)0.5-1.8 cm long, highly dependent on size of leaves, pubescent like the stems and leaves. Inflorescences opposite the leaves or very occasionally internodal, unbranched or occasionally forked, 1-4 cm long, with 2-6 flowers clustered at the tips of the branches, moderately pubescent with eglandular transparent or translucent simple uniseriate trichomes ca. 1 mm long, these appressed or spreading; peduncle 0.9-3.8 cm long; pedicels 0.8-1.4 cm long, ca. 0.5 mm in diameter at the base, ca. 1.5 mm in diameter at the apex, moderately to sparsely pubescent with trichomes like the rest of the inflorescence, articulated at the base; pedicel scars tightly packed at the inflorescence branch tips to the lowermost ca. 1 mm distant. Buds globose to broadly elliptic, the corolla included within the calyx lobes until just before anthesis, densely white-pubescent. Flowers 5-merous, cosexual (hermaphroditic). Calyx tube 1.5-3 mm long, elongate cup-shaped, the lobes 1.5-4 mm long, 1.2-2 mm wide, triangular to somewhat spathulate with a constricted base, moderately to sparsely pubescent with transparent to translucent eglandular simple uniseriate trichomes to 1 mm long, these spreading or somewhat appressed, the tip acute or rounded, the sinuses rounded. Corolla 1.5-2.5 cm in diameter, violet, pale violet or occasionally white, with a yellow-green or dark purple central star, stellate, lobed 2/3 to 3/4 of the way to the base, the lobes 7-10 mm long, 2.5-5 mm wide, spreading at anthesis, adaxially glabrous, abaxially densely pubescent-puberulent with white eglandular simple uniseriate trichomes to 1.2 mm long, longest along the petal midveins and at the tips, the pubescence especially obvious in buds. Stamens equal; filament tube minute; free portion of the filaments 1.5-2 mm long, sparsely pubescent adaxially with tangled transparent simple uniseriate trichomes; anthers 3.5-5 mm long, 1-1.5 mm wide, ellipsoid, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary conical, glabrous; style 8-10 mm long, straight, exserted beyond the anther cone, densely pubescent in the lower half with simple uniseriate trichomes; stigma capitate to slightly bilobed, the surface minutely papillate, green in live plants. Fruit a globose berry, (0.5)0.9-1 cm in diameter, green or greenish black when mature, the pericarp thin, matte, opaque, glabrous; fruiting pedicels 1.3-1.5 cm long, 0.7-1 mm in diameter at the base, 1.5-2 mm in diameter at the apex, not markedly woody, deflexed ("fruit hanging" fide Nee et al. 51880), not persistent; fruiting calyx slightly enlarging, the lobes ca. 6 mm long, ca. 3 mm wide, spreading with the tips reflexed. Seeds 10-20 per berry, ca. 1.5 mm long, ca. 1.2 mm wide, ovoid teardrop shaped, not markedly flattened, pale brownish yellow or straw-coloured, the surfaces minutely pitted, the testal cells pentagonal to rectangular in outline with strength walls. Stone cells 4-6(8) per berry, scattered through the mesocarp, ca. 0.5 mm in diameter, cream-coloured. Chromosome number: not known.

Distribution

(Fig. 46 ). Solanum dianthum occurs in the Andes of southern Peru (Dept. Cusco) and northern Bolivia (Depts. Cochabamba, La Paz, Santa Cruz).

Ecology and habitat.

Solanum dianthum grows in cloud forests, cloud forest margins and open grasslands at the edges of forests, often in tree falls or roadsides, from 1,640 to 3,900 m elevation.

Common names and uses.

None recorded.

Preliminary conservation status

( IUCN 2022). Least Concern [LC]. EOO = 79,792 km2 [LC]; AOO = 188 km2 [EN]. Like most morelloid species S. dianthum is a plant of open areas and has a relatively wide distribution. It occurs within protected areas in Bolivia (Area Natural de Manejo Integrado Apolobamba).

Discussion.

Solanum dianthum as circumscribed here is quite variable in pubescence, with some populations (notably those from around Unduavi, Bolivia) having loose spreading pubescence and somewhat more ovate leaves. Both this morphological variant and plants with appressed and somewhat strigose pubescence and more elliptic leaves are present on one of the sheets of the type collection (Bang 2492, NY, barcode 00139130). On an annotation slip on that sheet, C.V. Morton suggested that the small branch with looser pubescence in the centre of the sheet represented a different taxon. Examination of a range of specimens however suggest that this pubescence type grades into the more common appressed pubescence of the other sheets of Bang 2492, and that these collections, while on the face of it quite different in pubescence, are conspecific.

Solanum dianthum is somewhat similar morphologically to S. leptocaulon , but differs in its non-prostrate habit, stellate (versus campanulate) corollas and much larger anthers (3.5-5 mm long versus 2.5-3 mm long).

Most collections of S. dianthum have inflorescences opposite the leaves, but populations from around Siberia and Comarapa (Santa Cruz/Cochabamba, Bolivia) more or less uniformly have internodal inflorescences and white flowers with apparently reflexed corolla lobes at anthesis (e.g., Nee & Solomon 34074, Davidson 3852). These specimens are reminiscent of S. subtusviolaceum , but not glandular, and have the elongate calyx tube and slightly spathulate calyx lobes of S. dianthum . One of these collections, Steinbach 231, said on the label to be from "Angostura, Cercado de Santa Cruz 550m" is certainly mislabelled and instead is from Angostura in Prov. Cercado (Cochabamba) near the city of Cochabamba. Several collections from the northern part of the range have extremely large leaves and more robust, branched inflorescences than other collections of S. dianthum ; these do, however, fall within the range of flower and fruit morphology for the species (e.g., Lewis 88996, Valenzuela et al. 5933). Further geographical sampling and molecular assessment across the entire range of S. dianthum as defined here will certainly clarify this complex set of morphologies.

Solanum dianthum was described using the collection Bang 2492, which has two duplicates in NY. One of these has a branch of apparently different material glued in the centre of the sheet (NY barcode 00139130), while the other is clearly from a single plant (NY barcode 00139131). Although the first of these has Bang’s original field label, we select the second (NY barcode 00139131) as the lectotype of S. dianthum in case future taxonomists feel the branch in the centre does represent a different species (see discussion above).

Bitter (1912b) described S. hylobium using Buchtien 768, but without citing a herbarium. We here select the best preserved of the duplicates we have seen (US, barcode 00027609, acc. # 1176007) as the lectotype of this name. The sheet is annotated as " Solanum hylobium Bitt., n. sp." in Buchtien’s hand. Another sheet with the collection number Buchtien 768 in US (barcode 02054047, acc. # 1177099) is not Solanum , but is instead a specimen of Desmodium tortuosum (Sw.) DC. ( Leguminosae ) from a different locality "Millegasaya in Nord-Yungas" and different date “1917/XII”.

Figures

Figure 44. Solanum dianthum A habit B detail of adaxial leaf surface C detail of abaxial leaf surface D flower bud E dissected flower F fruiting branch G maturing fruit (A-F Steinbach 231). Illustration by R. Wise.

Figure 45. Solanum dianthum A habit B, C flowers at anthesis D developing fruits (A-D Nee et al. 55311). Photos by S. Stern.

Figure 46. Distribution map of Solanum dianthum.