A two-part study of tropical plant species related to potatoes, emphasizing questions of phylogenetic relationship and processes of evolutionary change, will be conducted by Drs. Greg Anderson and Robert Jansen of the University of Connecticut. They will generate a large data set of characters pertaining to chloroplast DNA and nuclear ribosomal DNA. These and other data will be used to construct a tree or cladogram of putative genealogical relationships of Solanum section Basarthrum species. A second series of studies will provide data bearing on hypothesized mechanisms of evolutionary change, data from morphology, breeding systems, geographical distribution, and chromosome composition. These process-oriented studies should help in understanding how the phylogenetic patterns were created. The studies focus upon a group of approximately 25 species that are native to the high mountains of Latin America and are closely related to potatoes. The group also includes the "pepino dulce," an Andean species domesticated for its fruit. Taxonomic relationships of the pepino are unclear and its origin unknown; thus, the study will benefit crop improvement by locating sources of useful traits that can be incorporated into the cultivated varieties. In addition the study will help explain the origins of dioecious solanums, species with separate male (pollen) and female (ovule) plants, an otherwise unusual breeding system in the genus.
