WILLIAMS, RACHEL A.* and L. ALAN PRATHER. Herbarium and Department of Botany & Plant Pathology, Michigan State University, East Lansing, MI 48824-1312. - Evolutionary relationships of the Clinopodioid complex and allied genera (Lamiaceae: Nepetoideae) based on ITS sequence data.
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