Evolutionary relationships of Solanum series Piurana and related species in Solanum section Petota (wild potatoes)

There are about 190 wild potato species (Solanum L. section Petota Dumort.) and their morphological similarity has led to widely conflicting taxonomic treatments. Solanum series Piurana Hawkes is one of 21 series recognized in section Petota in the latest comprehensive taxonomic treatment by Hawkes in 1990. They are distributed from southern Colombia, south through Ecuador to central Peru. The limits of the series and validity of its constituent species were unresolved. The present study integrated a phenetic morphological, a plastid DNA variation and a molecular phylogenetic analysis based on five conserved ortholog regions in order to understand species boundaries and interrelationships of members of Solanum series Piurana. The integration of the studies supported that an expanded Solanum series Piurana is a monophyletic group. This expanded series Piurana includes species previously considered as members of the series but also species considered in other seven series (Coniciabaccata, Cuneoalata, Ingaefolia, Olmosiana, Simplicissima, Tuberosa and Yungasensa), suggesting the need to redefine the series classifications of prior authors in sect. Petota as they are not supported as natural groups. The species status for several taxa grouping within the Piurana clade was reconsidered based on a combination of a history-based (phylogenetic) species concept or a morphological species concept, and reduced these species from 37 to 29. It was also demonstrated that the relationship among members of the Piurana clade is mostly supported by the presence of moniliform tubers and coriaceous leaves.