The Labiatae (mint family), one of the largest families of flowering plants, is of considerable medical and commercial importance because of the aromatic oils (terpenoids) that occur in the foliage of many species. The ongoing search for useful plant products in this and other related families is greatly facilitated by an understanding of evolutionary relationships among the species. A taxonomic classification that reflects evolutionary (that is, genealogical) history is likely to help researchers predict the occurrence of attributes (including useful chemical compounds) on the basis of the known distribution of similar attributes elsewhere in the family. The current classification of the mint family is based heavily on work done over a century ago and is founded on the assumption that the family is a natural group that likely evolved from a single source in the Verbenaceae (teak) family. This long-standing premise is contradicted by recent research by Dr. Philip Cantino at Ohio University, which suggests that the mints have evolved from several different subgroups of the tropical Verbenaceae alliance. A primary objective of the proposed research is to test this hypothesis using a computer analysis of the distribution of a wide variety of morphological characteristics in both families, with special emphasis on new pollen data derived from light- and scanning electron microscopy. Integration of the pollen data with evidence from leaf, stem, flower, and fruit morphology will make it possible to resolve the evolutionary relationships among the major groups of genera of Labiatae and Verbenaceae. This will represent a major step toward a more predictive and useful classification of both families, which in turn will facilitate the search for new, terpenoid characters.
