Subfamily Nepetoideae is the largest and most economically important subfamily of the Lamiaceae. Prior studies have supported the monophyly of the subfamily and a study based on cpDNA restriction site data identified a clade of several genera in tribe Mentheae, including Blephilia, Calamintha, Clinopodium, Monarda, and Hedeoma, that have apparently undergone a rapid diversification. This clade of 11 genera includes some that have been collectively referred to as the 'Clinopodioid complex'. The cpDNA restriction site study provided very little resolution of the relationships between these taxa. Here we use ITS sequence data to study the relationships of these eleven genera plus several additional ones that we have identified as belonging to this clade. The ITS data provided variation that yielded substantial resolution among these taxa. Preliminary results from the phylogenetic analysis indicate that several genera are non-monophyletic. Furthermore, many of the characters that are used to circumscribe genera in this complex, such as stamen number and calyx shape, are highly homoplasious. Our data suggest that Clinopodium, Hedeoma, and Monardella are non-monophyletic, and that Blephilia, Monarda, and Pycnanthemum are monophyletic. Major clades in this group are biogeographically cohesive.

Key words: Clinopodium, homoplasy, ITS sequence data, Lamiaceae, molecular phylogeny, Nepetoideae