Solanaceae Source

A global taxonomic resource for the nightshade family

Revision of Solanum ×aemulans from Thu, 2013-12-19 16:27

Citation author: 
Bitter & Wittm.
Citation: 
Bot. Jahrb. Syst. 50, Beibl. 553. 1914.
Type: 
Argentina. La Rioja: Dept. Famatina, Sierra de Famatina, La Encriciada, 29 Jan – 2 Feb 1879, G.H.E.W. Hieronymus & G. Niederlein 474 (lectotype, G00074133, upper plant [Correll neg. 320, F, LL, MO-5594448, NY, UC1152160], designated by Hawkes and Hjerting, 1969: 259; isolectotypes, B, destroyed [F neg. 2760, F-621202, NY, MO-1690843], G [Correll neg. 321, F-160375, LL, NY, UC1152160]).
Last edited by: 
Spooner, D.M.
Written by: 
Spooner, D.M. & A. Clausen
Habit: 
Herbs 0.1-0.3 m tall, rosette-forming to semierect. Stems 2-4 mm in diameter at base of plant, green, unwinged, subglabrous to moderately pubescent with short multicellular hairs; tubers typically orne singly at the end of each stolon.
Sympodial structure: 
Sympodial units tri- to plurifoliate, not geminate.
Leaves: 
Leaves odd-pinnate, the blades 9.5-29.5 x 1.7-9.2 cm, green, membranous to chartaceous, subglabrous to moderately pubescent adaxially and abaxially with hairs like those of the stems; lateral leaflet pairs 3-6, subequal except for the most proximal 1 or 2 pairs that are greatly reduced in size to unequal with the uppermost pairs clearly larger; most distal lateral leaflets 1.1-6.1 x 0.6-2.8 cm, broadly ovate to broadly elliptic, the apex acute to obtuse, the base typically oblique to cuneate, sessile and broadly decurrent to petiolulate with the petiolules up to 2 mm long; terminal leaflet 2.6-8.3 x 1.7-5.2 cm, orbicular to very broadly obovate, the apex rounded to obtuse, the base truncate to cuneate; interjected leaflets 0-5, sessile to short petiolulate, ovate to orbicular; petioles 1-5.5 cm, subglabrous to moderately pubescent with hairs like the stems. Pseudostipules absent to minute and scale-like to 1 mm long, pubescent with hairs like those of the stem.
Inflorescences: 
Inflorescences 1-3.5 cm, often near the base of the plant but sometimes in the distal half of the plant, generally unforked, with 1-5 flowers, with all flowers apparently perfect, the axes pubescent with hairs like those of the stem; peduncle highly contracted, sessile to 0.1 cm long, but sometimes longer to 1.8 cm long; pedicels 10-45 mm long in flower and fruit, spaced 1-10 mm apart, articulated high in the distal half.
Flowers: 
Flowers homostylous, 5-merous. Calyx 3-5 mm long, the tube 1-2 mm, the lobes 1-4 mm, acute to acuminate, the acumens 1-3 mm long, pubescent with hairs like those of the stem. Corolla 1.4-3.5 cm in diameter, rotate to rotate-pentagonal, blue adaxially and abaxially, the tube 1-2 mm long, the acumens 0-2 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 2.5-6 mm long, lanceolate, connivent, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary glabrous; style 6.5-10 mm x ca. 1 mm, exceeding stamens by 2-4 mm, straight, glabrous; stigma clavate to capitate.
Fruits: 
Fruit a globose to slightly ovoid berry, 1-2 cm wide, 1-2.2 cm long, green to green and purple mottled when ripe, glabrous.
Seeds: 
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 = 3x = 48 voucher: Okada 6769 (BAL) (Hijmans, et al. 2007)
2n = 4x = 48 voucher: Okada 6055 (BAL) (Hijmans, et al. 2007)

Distribution: 

Solanum ×aemulans is found in northern Argentina (Provs. Jujuy, Salta and La Rioja), in generally dry rocky areas, in railway embankments, among spiny shrubs or cacti, at the edges of cultivated fields or roadsides, along streamsides and ditches, close to stone walls of cattle enclosures as well as on bare soil; (2690) 3000-4000 (4020) m in elevation.

Phenology: 
Flowering and fruiting from January to April.
Phylogeny: 

Solanum ×aemulans is a member of Solanum sect. Petota Dumort., the tuber-bearing cultivated and wild potatoes. Within sect. Petota, Solanum ×aemulans 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-named Potato Clade, a group of perhaps 200-300 species that also includes the tomato and its wild relatives (Bohs, 2005).

Commentary: 

Solanum ×aemulans is distributed in two disjunct areas of Argentina in 1) Jujuy and Salta Provinces, 2) La Rioja Province. Triploid and tetraploid cytotypes are found in the northern range of its distribution (Jujuy and Salta), while only tetraploids occur in the Province of La Rioja. This species is frequently found growing with the following tuber-bearing species: S. acaule, S. oplocense, S. infundibuliforme, S. boliviense and S. brevicaule.

Solanum ×aemulans can be differentiated from S. acaule by the presence of the articulated pedicel, by its larger stamens, and frequently by the strong scent of the leaves. From S. megistacrolobum it can be differentiated by the number of lateral leaflets and by the rotate to rotate pentagonal corollas. From S. ×viirsooi it can be differentiated by the broadly ovate to lateral leaflets and by the rounded apex of the terminal leaflet.

A natural triploid hybrid of S. acaule × S. boliviense (referred to as S. megistacrolobum) was described by Okada and Clausen (1982) as S. ×indunii, as this nothospecies possesses characters of both parental species and co-occurs with them. These populations are common in northwest Argentina and were differentiated from S. acaule ssp. aemulans on the basis of minor morphological characters. Furthermore, these authors pointed out that the populations from Tilcara (Jujuy Province) of S. acaule ssp. aemulans and the hybrids of S. acaule x S. megistacrolobum had characters in common which could be interpreted as having a similar origin through the functioning of 2n gametes that could have resulted in a fertile hybrid tetraploid. Hosaka and Spooner (1992) were able to differentiate the two disjunct populations of aemulans on the basis of single-to low-copy nuclear DNA, but Nakagawa et al. (2002) could distinguish these on the basis of plastid DNA restriction site data.

We group the triploids (S. ×indunii) and tetraploids (S. ×aemulans ) together because of likely common origins and because they are morphologically indistinguishable, and we group the two sets of tetraploids together because they are morphologically indistinguishable. However, S. boliviense does not occur in the southern distribution range in La Rioja Province and as mentioned above they can be distinguished with plastid and nuclear DNA markers. Hawkes and Hjerting (1989) consider S. acaule not very closely related to any other wild potato species, although they point out similarities with species of the series Megistacroloba. They agree with Okada and Clausen (1982) in their interpretation of the hybrid origin of aemulans from Tilcara but consider that this interpretation is not valid for the type material from La Rioja, since S. megistacrolobum has not been found there.

References: 

Hawkes, J.G. & J.P. Hjerting 1969. The potatoes of Argentina, Brazil, Paraguay and Uruguay: a biosystematic study.
Oxford Univ. Press, Oxford, UK.

Okada, K.A. & A.M. Clausen 1982. Natural hybridization between Solanum acaule Bitt. and S. megistacrolobum Bitt. in the Province of Jujuy, Salta.
Euphytica 31: 817-835.

Hawkes, J.G. & J.P. Hjerting 1989. The potatoes of Bolivia: their breeding value and evolutionary relationships.
Oxford University Press, Oxford.

Hosaka, K. & D.M. Spooner 1992. RFLP analysis of the wild potato species, Solanum acaule Bitter (Solanum sect. Petota).
Theor Appl Genet 84: 851-858.

Nakagawa, K., H. Uehara & K. Hosaka 2000. Chloroplast DNA variation in the wild potato species, Solanum acaule and S. albicans.
Euphytica 116: 197-202.

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.

Taxonomic name: 
Solanum ×aemulans (Solanaceae)
Wed, 2013-11-20 10:57 -- sandy
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