Solanaceae Source

A global taxonomic resource for the nightshade family

Revision of Solanum medians from Thu, 2013-12-19 16:20

Citation author: 
Repert. Spec. Nov. Regni Veg. 11: 366. 1912.
Peru. Lima: hills of Mongomarca, loma formation, [Cerro de Amancaes], 500-600 m, 14 Aug 1910, A. Weberbauer 5683 (E. Seler 260) (holotype, B, destroyed [F neg. 2623, F-647974, G, MO-1691266, NY]; isotypes, CUZ, F-628465 [Correll neg. 52, F-1243698, F-1593165, F-1604849, G, LL, MO-5588448, NY, PTIS, UC1152337] GH00077717 [Correll neg. 733, LL, NY, PTIS, UC1152337], GOET [drawing, Correll neg. 730, F-1603855, LL, MO-5588447, NY, UC1152337], US00027676 [Correll neg. 734, LL, NY, PTIS, UC1152337]).
Last edited by: 
Spooner, D.M.
Written by: 
Spooner, D.M. & A. Clausen
Herbs 0.2-0.6 m tall, erect. Stems 3-5 mm in diameter at base of plant, dark green, sometimes tinged with purple, unwinged or with wings to 1 mm wide, coarsely pilose with typically whitish non-glandular erect trichomes; tubers typically borne singly at the end of each stolon.
Sympodial structure: 
Sympodial units tri- to plurifoliate, not geminate.
Leaves odd-pinnate, the blades 8-15 x 5-15 cm, medium to dark green and sometimes tinged with purple abaxially, membranous to chartaceous, moderately pubescent adaxially and abaxially with hairs like the stems; lateral leaflet pairs 1-4, greatly subequal and rapidly decreasing in size to the base; most distal lateral leaflets 1.5-10 x 0.4-8 cm, narrowly to broadly ovate to more rarely orbicular, the apex typically acute to acuminate to more rarely rounded and apiculate, the base typically sessile and short to widely decurrent on the basiscopic side to more rarely short-petiolulate; terminal leaflet 3-14 x 1-8 cm, narrowly to broadly ovate to more rarely orbicular, the apex typically acute to acuminate to more rarely rounded and apiculate, the base attenuate; interjected leaflets 0-7, sessile to short petiolulate, ovate to orbicular; petioles 0.7-3 cm, coarsely pilose with typically whitish non-glandular erect trichomes. Pseudostipules minute to 12 mm long, lunate, coarsely pilose with typically whitish non-glandular erect trichomes.
Inflorescences 2.5-10 cm, terminal with a subtending axillary bud, generally in distal half of the plant, usually forked, with 5-15 flowers, with all flowers apparently perfect, the axes pubescent with hairs like those of the stem; peduncle 1.3-8 cm long; pedicels 1.5-8 mm long in flower and fruit, spaced 1-10 mm apart, articulated typically in the distal half.
Flowers homostylous, 5-merous. Calyx 6-11 mm long, the tube 1-2 mm, the lobes 3-5 mm, linear to long attenuate, the acumens 2-4 mm long, pubescent with hairs like those of the stem. Corolla 2.8-3.5 cm in diameter, pentagonal to rotate, dark blue to violet and typically with a green central star adaxially and abaxially, the tube 1-2 mm long, the acumens 1-1.5 mm long, the corolla edges flat, not folded dorsally, glabrous abaxially, minutely puberulent adaxially, especially along the midribs, ciliate at the margins, especially at the tips of the corollas. Stamens with the filaments 1-2 mm long; anthers 4-7 mm long, lanceolate, connivent, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary glabrous; style 8-9 mm x ca. 1 mm, exceeding stamens by 2-4 mm, straight, glabrous; stigma clavate to capitate.
Fruit a globose to slightly ovoid berry, ca. 1.5 cm wide, 1.5-1.8 cm long, medium to deep green when ripe, often with scattered white dots, glabrous.
Seeds from living specimens ovoid and ca. 2 mm long, whitish to greenish in fresh condition and drying brownish, with a thick covering of “hair-like” lateral walls of the testal cells that make the seeds mucilaginous when wet, green-white throughout; testal cells honeycomb-shaped when lateral walls removed by enzyme digestion.
Chromosome number: 

2n = ploidy missing =24 voucher: Ochoa & Salas 7361 (CIP) (Hijmans, et al. 2007)
2n = 3x = 36 voucher: Ochoa & Salas 7304 (CIP) (Hijmans, et al. 2007)


Solanum medians is found from central Peru (Dept. Ancash) south to northern Chile in Regions I (Tarapacá) and II (Antofagasta), along the western slopes of the Andes; growing in a variety of sunny habitats along the dry coastal lomas to high frigid areas near snow fields and among Stipa ichu grasses in the puna. The most frequently mentioned habitat characteristics are apparently poor soils in rocky and sandy areas, but it has been collected along field margins and streamsides; 200-3800 m in elevation.

Flowering and fruiting along the coast from May to October, and in the higher Andes from November to April.

Solanum medians is a member of Solanum sect. Petota Dumort., the tuber-bearing cultivated and wild potatoes. Within sect. Petota, Solanum medians is a member of a very diverse clade related to the cultivated potato. On a higher taxonomic level, it is a member of the informally-names Potato Clade, a group of perhaps 200-300 species that also includes the tomato and its wild relatives (Bohs, 2005).


Solanum medians is morphologically very similar to some populations of S. oplocense Hawkes, an inland species ranging from central Bolivia to northern Argentina. Correll (1962: 512) identified some collections from Bolivia as S. tacnaense var. sandemanii that we examined and identify as S. oplocense. Both species share similar pubescence, leaf shape, and corolla morphology. Solanum oplocense, however, generally has pedicel articulation at or below the middle, and S. medians is distinct based on AFLP data (Spooner et al. 2005).

No herbarium was designated for the type of S. weberbaueri var. poscoanum. The label states “Herbarium Vargasianum, Universidad del Cuzco,” and Correll’s labels distributed with his photos of these plants state the specimen was at herbarium CUZ, but the only specimen we found was at K. Ochoa (1999) lists specimens in CPC (Commonwealth Potato Collection at Dundee, Scotland) and his personal herbarium. The CPC has distributed all of its specimens, and Ochoa has distributed his herbarium widely, but mostly to CUZ. We found no isolectotype at CUZ on our visits in 2006 and 2007.

Hawkes (1954) designated F.W. Pennell 13196 at K as holotype for S. sandemanii. We have not located this specimen but have seen photos of it as listed above. Ochoa (1999) invalidly designated a specimen of F.W. Pennell 13196 at F as lectotype of S. sandemanii.


Hawkes, J.G. 1954. New Solanum species in sub-section Hyperbasarthrum Bitt.
Annals and Magazine of Natural History, including zoology, botany, and geology. London. Ser. 12(7): 689-710.

Ochoa, C.M. 1999. Las papas de sudamerica: Peru (Parte I).
Lima, Peru: International Potato Center.

Spooner, D.M., K. Mclean, G. Ramsay, R. Waugh, & G.J. Bryan 2005. A single domestication for potato based on multilocus AFLP genotyping.
Proc. Natl. Acad. Sci. USA. 120: 14694-14699.

Bohs, L. 2005. Major clades in Solanum based on ndhF sequences.
Pp. 27-49 in R. C. Keating, V. C. Hollowell, & T. B. Croat (eds.), A festschrift for William G. D’Arcy: the legacy of a taxonomist. Monographs in Systematic Botany from the Missouri Botanical Garden, Vol. 104. Missouri Botanical Garden Press, St. Louis.

Hijmans, R., T. Gavrilenko, S. Stephenson, J. Bamberg, A. Salas & D.M. Spooner 2007. Geographic and environmental range expansion through polyploidy in wild potatoes (Solanum section Petota).
Global Ecol. Biogeogr. 16: 485-495.

Spooner, D.M., D. Fajardo & A. Salas 2008. Revision of the Solanum medians complex (Solanum sect. Petota).
Syst. Bot. 33: 579-588.

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