LEE, JOONGKU1*, BRUCE G. BALDWIN1, and L. D. GOTTLIEB2. 1Jepson Herbarium and Department of Integrative Biology, University of California, Berkeley, CA 94720; 2Section of Evolution and Ecology, University of California, Davis, CA 95616. - A molecular phylogenetic reexamination of the western North American subtribes Stephanomeriinae and Microseridinae (Compositae--Lactuceae).
Phylogenetic analysis of sequences of the ITS and ETS regions of
18S-26S nuclear rDNA for all genera of Stephanomeriinae (sensu
Stebbins) except Thamnoseris and all of Microseridinae (sensu
Stebbins) reveals that both subtribes are unnatural and identifies a
series of subclades, each with very strong bootstrap support (greater
than 96%). Subclade 1: Munzothamnus, Pleiacanthus,
Rafinesquia, and Stephanomeria, all with x=8, and
Prenanthella with n=7. Subclade 2: Agoseris,
Microseris, Nothocalais, Uropappus, and
Stebbinsoseris. Subclade 3: Lygodesmia (sensu Tomb),
Chaetadelpha, both with n=9, and the annual
Shinnersoseris with n=6. Subclade 4: the recently
discovered monotypic Marshalljohnstonia, a rosette-shrub from
northern Mexico, and Pinaropappus, a genus of perennial herbs
also found in Mexico. Several additional, well-supported subclades can
be recognized, each including some species of Malacothrix
(sensu lato), a genus now seen as polyphyletic with quite disparate
elements. Partitioning of the two subtribes into smaller subclades
greatly simplifies the relationships among these genera. Considered as
a group, the 24 genera examined represent a single, major radiation of
Lactuceae mostly confined to western North America.
Key words: Compositae, ETS, ITS, Lactuceae, Microseridinae, Stephanomeriinae