Phylogenetic relationships of wild potatoes, Solanum series Conicibaccata (sect. Petota)

Solanum sect. Petota series Conicibaccata is a group of 40 wild potato species, composed of diploids, tetraploids, and hexaploids, distributed from central Mexico to central Bolivia. This study examined their species boundaries and interrelationships by phenetic analyses of morphological data and cladistic analyses of chloroplast DNA restriction site data. Mitotic chromosome counts were obtained for 114 accessions; species whose first counts are reported here are S. garcia-barrigae, S. orocense, and S. sucubunense. Most results were concordant in showing three main groups of species: 1) tetraploids and hexaploids from central Mexico to southern Ecuador; 2) diploids from northern Peru to Bolivia, included in a cpDNA clade of diploids and hexaploids assigned to ser. Demissa and ser. Tuberosa, and 3) diploids and tetraploids from southern Colombia to Peru, cladistically related to members of ser. Piurana. Some species boundaries, and even series boundaries of ser. Conicibaccata and ser. Piurana, are supported morphologically only by a combination of widely overlapping character states, none of which is constant for a species. Other species have no support, and it is Likely that too many species are recognized in the group. The cladistic analysis of chloroplast DNA data suggested that some species represent a combination of apospecies and plesiospecies, and some populations are of possible hybrid origin.