A CHLOROPLAST DNA PHYLOGENY OF THE SOLANACEAE - SUBFAMILIAL RELATIONSHIPS AND CHARACTER EVOLUTION

Phylogenetic relationships among 42 species of Solanaceae representing 12 of the 14 currently recognized tribes were assessed by chloroplast DNA restriction site mapping. Over 1,000 cleavage sites were identified for 10 restriction enzymes and of these, 447 provided information concerning relationships among the included taxa and the outgroup, Ipomoea (Convolvulaceae). The results establish that subfamily Cestroideae is ancestral in the family and is paraphyletic, and that the subfamily Solanoideae is derived from within the Cestroideae and is monophyletic, if it is circumscribed to include Nolana. The tribe Salpiglossideae, characterized by floral zygomorphy and reduction in stamen number, is.probably polyphyletic and hence artificial. An analysis of character evolution in the family suggests that the tribe Nicotianeae retains the most primitive morphological characters of any tribe in the family and helps to explain the disjoint position of members of the tribe in two distinct lineages in the Cestroideae. The chromosome base number x = 12 unites the Solanoideae with the Anthocercideae and Nicotiana. The worldwide distribution of the Solanoideae versus the almost exclusively New World distribution of the Cestroideae argues for a predominantly long-distance dispersal, rather than a vicariance explanation of biogeographic distributions in the family. The morphologically distinctive genus Schizanthus is the earliest diverging lineage in the family. Tribal relationships within the Solanoideae remain poorly resolved and await more detailed study.