COMBINING DATA IN PHYLOGENETIC SYSTEMATICS - AN EMPIRICAL-APPROACH USING 3 MOLECULAR-DATA SETS IN THE SOLANACEAE

Data from sequences of two chloroplast DNA (cpDNA) genes, ndhF and rbcL, and from restriction site mapping studies of the entire chloroplast genome were analyzed for the same set of 17 species of Solanaceae (potato/tomato family) and the outgroup Ipomoea (Convolvulaceae, morning glory family). ndhF is a more rapidly evolving gene and yields more phylogenetic information than does rbcL. The results of analyses of each data source independently are congruent with respect to certain major features of Solanaceae phylogeny but are in conflict with respect to the branching order within the monophyletic subfamily Solanoideae. This conflict resides in a portion of the phylogeny where relatively few characters are available in any of the three data sets. Combining the data into a single analysis yielded a more fully resolved tree, in which some clades are supported that are unique to each individual data set. However, in each such case, these resolved clades also were obtained when the two alternative data sets were analyzed together. The analysis of the combined data set provides substantial support for increased resolution within the Solanoideae and for the rest of the tree. The ''X = 12'' clade, so called because of a base chromosome number synapomorphy, comprises the subfamily Solanoideae, tribe Anthocercideae, and part of tribe Nicotianeae (Nicotiana) and is the most well-supported clade within the family.