COLLAPSE OF MORPHOLOGICAL SPECIES IN THE WILD POTATO SOLANUM BREVICAULE COMPLEX (SOLANACEAE, SECT. PETOTA)

The major cultivated potato, Solanum tuberosum, and six other related cultivated species, are hypothesized to have arisen from a group of we edy relatives indigenous to the central Andes of central Peru, Bolivia , and northern Argentina. A major problem hindering investigations of the origins of the cultivated species has been a continuing debate ove r the species boundaries of their putative progenitors. This study inv estigated the morphological phenetic species boundaries of these putat ive progenitors and five cultivated taxa, here collectively referred t o as the Solanum brevicaule complex. Two hundred fifteen accessions of 30 taxa in the S. brevicaule complex and 42 accessions of six taxa ou tside of the complex were assessed for 53 morphological traits in repl icate plots ina common garden, resulting in a total of over 81000 data points. Phenetic analyses of these data are unable to support 30 taxa , suggesting instead a single variable complex at best only weakly div ided into three widely intergrading sets of populations: (1) Peruvian and geographically adjacent Bolivian accessions (including wild specie s and all the cultigens), (2) Bolivian and Argentinian accessions and S. verrucosum from Mexico (including only wild species), and (3) the B olivian and Argentinian wild species S. oplocense. These and other dat a suggest that Hawkes's 1990 treatment (The Potato: Evolution, Biodive rsity, and Genetic Resources, Smithsonian Institute Press, Washington, DC.) of 232 morphological species is an overestimate for sect. Petota .