2n = ploidy missing =24 voucher missing = (Spooner & Hijmans 2001)
Widespread throughout central Mexico (Jalisco to Querétaro and Hidalgo) to southern Mexico (Oaxaca), 1900-2900 m; deciduous tropical forests, fallow fields, in grassy areas among bushes, Agave, and Opuntia and along fencerows, in areas of fir, oak, and pine forest.
Solanum polyadenium belongs to the potato clade of Solanum (Bohs, in press). Spooner and Sytsma (1992) placed S. polyadenium 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. Spooner et al. (2004) placed S. lesteri and S. polyadenium in the Polyadenia group. Solanum lesteri and S. polyadenium clearly are sister taxa that are united by cpDNA data (Spooner and Sytsma 1992), morphological data (Lara-Cabrera and Spooner, in press a) and AFLP data (Lara-Cabrera and Spooner, in press b). As a group they are very easily distinguished in the field by their highly glandular leaves with Type A (short-stalked glandular) trichomes, their characteristic strong “mousy” odor, and on herbarium specimens with a yellowish or yellow-brown color to the foliage (green in other species).
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.
Hawkes, J.G. 1990. The potato: evolution, biodiversity and genetic resources.
Oxford: Belhaven Press.
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.
Syst. Bot. 17:432-448.
Spooner, D.M. & R.J. Hijmans 2001. Potato systematics and germplasm collecting, 1989-2000.
Amer. J. Potato Res. 78:237-268; 395.
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.
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.
Syst. Bot. Monog. 68: 1-209 + 9 plates.
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).
Solanum polyadenium is easily distinguished in the field by its highly glandular leaves with a dense covering of Type A (short-stalked) trichomes, its characteristic strong “mousy” odor, and on herbarium specimens with a yellowish or yellow-brown color to the foliage. It could be confused with S. lesteri. Hawkes (1990) distinguished S. lesteri from S. polyadenium by its “dense indumentum of long spreading multicellular hairs on all green parts, in addition to the glandular ones,” and conical fruits, in contrast to S. polyadenium with the “the whole plant covered with very frequent stalked glands” and “very sparse multicellular non-glandular hairs,” and ovoid fruits. Examination of living representatives of these two species in Sturgeon Bay in 2001 by Spooner et al. (2004) showed great variation in S. lesteri; Hawkes et al. 1714 and Spooner et al. 4177 had the dense non-glandular hairs, but Spooner et al. 4155 had much less non-glandular pubescence more typical of S. polyadenium. In addition, some isotype specimens of S. polyadenium had a dense indumentum of non-glandular hairs. The only trait Spooner et al. (2004) could find to separate these species, therefore, was fruit shape.
This fruit shape difference is not so evident, however, as the types of both S. polyadenium and its synonym S. polyadenium subsp. orizabae have short, triangular fruits, as do some other populations cited by Spooner et al. (2004). Not all herbarium specimens of either species have mature fruits. Solanum lesteri appears as an extreme, long triangular fruit variant of S. polyadenium. Their distribution pattern (S. lesteri at the southern end of the range of S. polyadenium) could argue for varietal or subspecies status for S. lesteri. Chloroplast DNA restriction site data (Spooner and Sytsma 1992) showed the two species to be united by 11 synapomorphies, but for the single population of S. lesteri to be distinguished from the three populations of S. polyadenium by three autapomorphies. Spooner et al. (2004) maintained them as separate because of the stark distinction of the fruit shapes in most specimens, but additional field and molecular studies may indicate that they intergrade more than is apparent here suggesting that one species is warranted.