Submitted to: Systematic Botany
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/3/2007
Publication Date: 11/2/2007
Citation: Fajardo, D., Castillo, R., Salas, A., Spooner, D.M. 2007. A morphometric study of species boundaries of Solanum series Conicibaccata: a replicated field trial in Andean Peru. Systematic Botany. 33:183-192. Interpretive Summary: There are about 200 species of wild potatoes widely distributed throughout the Americas from the southwestern United States south to Argentina, Chile, and Uruguay. Many of these species are very similar to each other and they may not all be worthy of recognition as valid species. This study studies the validity of recognizing species for a group of 40 of these wild potatoes, technically known Solanum series Conicibaccata. They grow from southern Mexico to central Bolivia. It studies their species status by using the overall form of the plant (morphological data) from an area in the central Peruvian Andes, and compares these data to a prior study of the group from the United States. Both the US and Peruvian studies can distinguish groups of species that are diploid (two sets of chromosomes) from polyploids (multiple sets of chromosomes), but many species within these chromosome groups are difficult to recognize. We conclude that there likely are fewer species in series Conicibaccata. Because species names are used to make inferences on their use, as in potato breeding programs, this study helps us to make better inferences about the useful traits of this species.
Technical Abstract: Solanum series Conicibaccata contains about 40 wild potato (section Petota) species distributed from southern Mexico to central Bolivia. It is defined by conical fruits and imparipinnate leaves with mostly parallel sides, but variation within and between other series makes it difficult to circumscribe. It contains diploids (2n = 2x =24), tetraploids (2n = 4x = 48) and hexaploids (2n = 6x = 72). Our morphological phenetic study in an Andean site in central Peru (12°S, 3200 m altitude) is a replicated study from the north central United States (45°N, 180 m elevation) but uses more species (27 vs. 25), accessions (175 vs. 100), and morphological characters (97 vs. 44). Cophenetic correlation coefficients using identical accessions and characters from the US/Peru is 0.62; identical US/Peru accessions and all Peruvian characters is 0.58; and of replicated trials in Peru is 0.56. Stepwise discriminate analyses between US/Peru supported three characters as most important to distinguish species: number of lateral leaflets, a fruit shape measure, and the width of wings on the stem. Both US and Peruvian studies provide phenetic support to separate the diploids from the polyploids, but suggest that many species need to be placed in synonymy.