Submitted to: Plant Systematics and Evolution
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/2/2007
Publication Date: 5/5/2008
Citation: Alvarez, N., Peralta, I., Salas, A., Spooner, D.M. 2008. A morphometric study of species boundaries of the wild potato Solanum brevicaule complex: replicated field trials in Argentina and Peru. Plant Systematics and Evolution. 274:37-45. Interpretive Summary: The Solanum brevicaule complex is the technical name for a group of about 20 wild potato species stributed in Peru, Bolivia, and Argentina. The complex is recognized as a group because these 20 look so similar that they may all be the same species, or at the minimum represent fewer than 20 species. In addition to their similarity among themselves, they look very similar to cultivated potatoes, and indeed the cultivated potato originated from the wild species of the Solanum brevicaule complex. This study examines if there are 20 species or fewer species by an examination of the form of these plants from two experimental field plots, one in the high Andes of central Peru, and another plot at the eastern base of the Andes in central Argentina. In addition, this study compares the results of these Peruvian and Argentinean studies with a prior study in the US, and with additional molecular studies of these same collections. The results of all studies support one group of species of the Solanum brevicaule complex from Peru, and another group of species from Argentina and Bolivia, but not 20 species. These results are important because they are being used to write a book on the potatoes of South America, and also are useful because they provide us better information on the diversity of the wild species that evolved into the cultivated potato.
Technical Abstract: The Solanum brevicaule complex is a group of about 20 wild potato species (sect. Petota), containing about 30 taxa with included subspecies and varieties. The complex is defined entirely by morphological similarity of its constituent members that are distributed from Peru south to central Argentina. They are very similar to each other and difficult to distinguish from some landraces of the cultivated potato, Solanum tuberosum. The complex contains diploids (2n = 2x =24), tetraploids (2n = 4x = 48) and hexaploids (2n = 6x = 72). Hybridization may be common among the species. Species boundaries are difficult to assess and conflicting taxonomic treatments are common among authors. Species boundaries within the complex have been studied with morphological phenetics from germplasm accessions planted in a field plot in the north central United States (45°N, 180 m elevation), and with molecular marker data from low-copy nuclear RFLPs, RAPDs, and AFLPs. The present study compares these results with two additional replicated morphological studies of the same germplasm accessions in a greenhouse environment in central Peru (12°S, 3200 m) and in a field plot in the west-central Argentina (33°S, 920 m). Correlation coefficients among all three morphological studies were low (0.29-0.32), and higher among molecular marker datasets (0.54-0.76). The results from the US and Peruvian (but not Argentinean) morphological data were similar in supporting three groups of species: (1) the “northern” S. brevicaule complex taxa from Peru and adjacent northwestern Bolivia, (2) the “southern” S. brevicaule complex taxa from Bolivia to Argentina, and (3) S. oplocense. The cultivars of S. tuberosum are clustered with the northern complex. There is poor support for species clustering within these northern and southern groups, suggesting the need for reduction of species in the complex.