2n = ploidy missing =24 voucher missing = (Spooner & Hijmans 2001)
U.S.A.: southern Utah and S Colorado, New Mexico, Arizona, southwestern Texas; Mexico: N Sonora and N Chihuahua, and disjunct populations in Querétaro and San Luis Potosí; among boulders on hillsides, sandy alluvial stream bottoms, in gravel along trails or roadways, rich organic soil of alluvial valleys, sandy fallow fields, grasslands, juniper-pinyon scrub deserts, oak thickets, coniferous and deciduous forests; 1370-2870 m.
Solanum jamesii belongs to the potato clade of Solanum (Bohs, in press). Spooner and Sytsma (1992) placed S. jamesii and all other North and Central American diploids (exclusive of S. bulbocastanum, S. cardiophyllum, and S. verrucosum) in the basal “clade 1” of section Petota based on chloroplast DNA restriction site data. These Mexican diploids were studied by Spooner and Lara-Cabrera with morphological and microsatellite data (Lara-Cabrera and Spooner, in press a) and AFLP data (Lara-Cabrera and Spooner in press b). Spooner et al. (2004) placed S. jamesii and S. pinnatisectum in the Pinnatisecta group. These are the only two species in sect. Petota with pinnatifid pseudostipules, and they are united by AFLP data (Lara Cabrera and Spooner, in press b).
Solanum jamesii is very similar to S. cardiophyllum, S. ehrenbergii and S. stenophyllidium. It is readily distinguished from them by its pinnatifid pseudostipules, a character shared only by S. pinnatisectum that has 6-8 pairs of lateral leaflets vs. 3-4 pairs for S. jamesii. All other wild potato species from North and Central America have lunate stipules.
The type sheet of S. jamesii bears two flowering specimens, one larger than the other; both comprise the holotype.
Bitter (1913) created Solanum jamesii subsp. septentrionale by combining S. jamesii var. heterotrichium, S. jamesii var. sinclarii, and S. jamesii var. brachistotrichium into a single subspecies. Spooner et al. (2004) considered the first and second of these names to be synonyms of S. jamesii, and the third to be a synonym of S. stenophyllidium. Bitter designated no type for this new name, but cited only the three varietal names. The types of these names, therefore, become syntypes from which a lectotype was chosen.
Records of S. jamesii from natural habitats in Colorado are limited to the extreme southwestern and southeastern parts of the state. Several disjunct populations from northern Colorado in Boulder and Larimer Counties and in Scottsbluff County Nebraska are near cultivated fields and greenhouses. Recent searches at these localities have been unsuccessful (Bamberg et al. 2003). These disjunct northern sites likely represent recent introductions to experimental stations.
Lara-Cabrera, S. & D.M. Spooner Taxonomy of Mexican diploid wild potato (Solanum sect. Petota) species: AFLP data.
Plant Syst. Evol.
Lara-Cabrera, S. & D.M. Spooner Taxonomy of Mexican diploid wild potato (Solanum sect. Petota) species: morphological and microsatellite data.
Monogr. Syst. Bot., Missouri Bot. Gard.
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Spooner, D.M. & K.J. Sytsma 1992. Reexamination of series relationships of Mexican and Central American wild potatoes (Solanum sect. Petota): evidence from chloroplast DNA restriction site variation.
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Spooner, D.M. & R.J. Hijmans 2001. Potato systematics and germplasm collecting, 1989-2000.
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Lara-Cabrera, S.I. 2001. Taxonomy of Mexican diploid wild potato (Solanum sect. Petota) species: a morphological and molecular study.
Ph.D. Thesis, Plant Breeding and Plant Genetics Program, University of Wisconsin-Madison.
Bamberg, J., A. del Rio, Z. Huamán, S. Vega, M. Martin, A. Salas, J. Pavek, S. Kiru, C. Fernandez, & D.M. Spooner 2003. A decade of collecting and research on wild potatoes of the southwest USA.
Amer. J. Potato Res. 80: 159-172.
Spooner, D.M., R.G. van den Berg, A. Rodríguez, J. Bamberg, R.J. Hijmans, & S.I. Lara-Cabrera 2004. Wild potatoes (Solanum section Petota; Solanaceae) of North and Central America.
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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.
Chloroplast DNA restriction site data available in: Spooner and Sytsma (1992). AFLP, morphological, and microsatellite data listed in: Lara-Cabrera (2001).