2n = 2x = 24 voucher: Spooner et al. 6714 (BOLV, PTIS, WAG, WIS) (Hijmans, et al. 2007)
Solanum circaeifolium is endemic to Bolivia, from Dept. La Paz south to Dept. Chuquisaca, occuring in a wide range of habitats, in full sun or in partial shade, typically in moist areas, on rocky slopes, among bushes, in scrub or thorn forests, in or at the edges of forests, in cultivated fields; 2000-4000 m in elevation.
Solanum circaeifolium is a member of Solanum sect. Petota Dumort., the tuber-bearing cultivated and wild potatoes. It possesses white stellate corollas and has a ploidy (EBN) of 2x (2EBN), features characteristic of species from Mexico and Central America, not of most species from South America. 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).
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.
Hawkes, J.G. & J.P. Hjerting 1989. The potatoes of Bolivia: their breeding value and evolutionary relationships. Oxford University Press, Oxford.
Hawkes, J.G. 1990. The potato: evolution, biodiversity and genetic resources. Oxford: Belhaven Press.
Ochoa, C.M. 1990. The potatoes of South America: Bolivia. Cambridge University Press, Cambridge, UK.
Spooner, D.M., R.G. van den Berg, W. García & M.L. Ugarte 1994. Bolivia potato collecting expeditions 1993, 1994: taxonomy and new germplasm resources. Euphytica 79:137-148.
Spooner, D.M. & S. Knapp. 2013. Solanum stipuloideum Rusby, the correct name for Solanum circaefolium Bitter. Am. J. Potato Res. (2013) 90:301–305.
Van den Berg, R.G. & N. Groendijk-Wilders 1999. Numerical analysis of the taxa of series Circaeifolia (Solanum sect. Petota). Pp. 213-226 In M. Nee, D. E. Symon, R. N. Lester, and J. P. Jessop (eds). Solanaceae IV: Advances in biology and utilization. The Royal Botanic Gardens, Kew, U.K.
Van den Berg, R.G., N. Groendijk-Wilders, M.J. Zevenbergen & D.M. Spooner 2001. Molecular systematics of Solanum series Circaeifolia (Solanum section Petota) based on AFLP and RAPD markers. pp. 72-84 In: R.G. van den Berg, G. Barendse, G. W. van der Weerden, and C. Mariani (eds.). Solanaceae V: Progress in taxonomy and utilization. Nijmegen Univ. Press, Nijmegen, The Netherlands.
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.
Jacobs, M.J., R.G. van den Berg, V.G.A.A. Vleeshouwers, M. Visser, R. Mank, M. Sengers, R. Hoekstra & B. Vosman 2008. AFLP analysis reveals lack of phylogenetic structure within Solanum section Petota. BMC Evol. Biol. 8, 145: 2-12.
Solanum stipuloideum is one of the most distinctive species in sect. Petota. Unlike many species in South America, it possesses white, stellate corollas. Its elliptic-conical fruits are somewhat similar to those of members of the Conicibaccata Group (e.g. S. colombianum Bitter), or to S. trifidum Correll from Mexico, but the fruits are narrower and distinctly pointed at the end.
Solanum stipuloideum was long known as S. circaefolium, but recent work in Solanum coupled with digitization of type specimens led to the discovery that a name commonly associated with the Morelloid clade (sensu Bohs 2005) was in fact a potato, and the oldest name for this taxon (Spooner & Knapp 2013).
Solanum stipuloideum has been treated in various ways (reviewed in Van den Berg & N. Groendijk-Wilders, 1999). The most recent treatments by Hawkes and Hjerting (1989) and Hawkes (1990) recognized three species and two varieties (S. circaeifolium subsp. circaeifolium and subsp. quimense, S. capsicibaccatum, and S. soestii), and Ochoa (1990) recognized two species and two varieties (S. circaeifolium var. circaeifolium and var. capsicibaccatum, and S. soestii). These authors emphasized leaf and calyx pubescence, terminal leaflet size and shape, peduncle and pedicel length, and corolla diameter as key characters to distinguish these taxa (Van den Berg & N. Groendijk-Wilders, 1999). Specimens of S. circaeifolium subsp. circaeifolium were identified as narrowly restricted to the extreme northern portion of the range near Lake Titicaca in Dept. La Paz, S. soestii to a single locality in southern La Paz Dept., and the other taxa more widespread and overlapping in range (Hawkes and Hjerting, 1989; Ochoa, 1990).
Van den Berg and Groendijk-Wilders (1999) evaluated the validity of these taxa with morphological data and Van den Berg et al. (2001) with RAPD and AFLP data. The morphological data documented extensive overlap of all 26 characters they analyzed but 18 of them showed statistically significant differences among taxa (0.05 level). The RAPD data distinguished S. soestii but not the other taxa and the AFLP data distinguished all of the taxa recognized by Hawkes and Hjerting (1989) and Hawkes (1990). However, a subsequent AFLP study by Jacobs et al. (2008), using a much wider range of species, supported all of these species as a distinct group, but failed to separate them into species-specific groups.
The type locality of S. stipuloideum is likely to be in the Department of La Paz; the printed locality on the label of the isotype (“Yungas”) is deliberately crossed out, and other Bang specimens with collection numbers near this one (e.g., Bang 2492, the type of S. dianthum Rusby) are from the province of Nor Yungas. It is, however, likely that this was caused by re-using existing labels for the specimens they distributed until they were gone.
Our examination of 96 herbarium specimens from throughout the range of these names show so much overlap of “taxon-specific” characters that identifications become impossible with morphological data. Only by reference to locality data could we identify S. circaeifolium subsp. circaeifolium and S. soestii, but not the other names that have no defined range. For example, Hawkes and Hjerting (1989) partly key out S. capsicibaccatum based on its non-acuminate leaflet apices. Yet this character is not clearly distinct, and both acute and acuminate leaflet apices occur on the types of all taxa recognized by the above authors, as well as specimens throughout the range of these names. We examined variation in leaf dissection that ranged from simple leaves (supposedly species-specific for S. circaeifolium subsp. circaeifolium and confined to the northern part of the range of all of these names) to 1-4-jugate leaves farther south. In the north, the specimens were mostly simple (rarely 1-jugate) but many populations to the south also had simple leaves (e.g., Brooke 3051, 3037, Solomon 17510). Solanum soestii is distinguished by lanceolate to linear-lanceolate leaflets with the terminal and lateral leaflets about the same size. We found no exact match for the type but there are many specimens similar with linear-lanceolate leaflets (e.g., Cárdenas 5519, Hjerting et al. 4486) and specimens with wider leaflets but of subequal size (e.g., Hawkes et al. 6578), and consider S. soestii to fall within the range of S. capsicibaccatum. In addition, a collection by Spooner et al. (1994) in Bolivia in 1993 at the sole known locality of S. soestii, Spooner et. al. 6722 (BOLV, PTIS, WAG, WIS), while a close match to the type, shows certain characters differing from the type. Most notably, some leaves have lateral leaflets decreasing in size towards the base, diverging from the subequal sizes described for the type.
In the protologue of Solanum capsicibaccatum two collection numbers, H. Gandarillas 60 and M. Cárdenas & H. Gandarillas 3600 are listed, but Gandarillas 60 at “Herbarium Cardenasianum” is clearly stated as the type. Cárdenas & Hawkes (1946) and Hawkes and Hjerting (1989) list the latter as type but this does not match the original publication. We have searched Bolivian herbaria BOLV, COCH, and LPB and did not locate Gandarillas 60. The GH specimen labeled “Herbarium Cardenasianum” is considered the holotype here.