Systematics Section / ASPT
Mayer, Michael .
Phylogeny of the Thelypodieae (Brassicaceae), based on ITS and ndhF sequence analysis.
Membership in the Thelypodieae and circumscription of its genera have long been contentious. Recent work by others has suggested that this tribe of new world mustards is paraphyletic, and includes many species and genera of other tribes. Moreover, my past work has hinted that the streptanthoid members of the tribe are not monophyletic. I report here that the combined analysis of ITS and ndhF sequences has begun to provide robust phylogenetic insight into the group: both Streptanthus and Caulanthus are polyphyletic; Caulostramina, Glaucocarpum, Iodanthus, Pringlea, and Sibaropsis are nested within the Thelypodieae clade; and I corroborate recent claims that new world Sisymbrium and its segregates (e.g., Schoenocrambe and Coelophragmus) arose from the Thelypodieae clade. These findings also force a reappraisal of traditional concepts of morphological evolution in the tribe. For example, my results reveal a basal rather than derived position of a Thelypodiopsis clade in the tribe. One of the implications of this topology is that the ancestral morphology in the Thelypodieae could have featured, instead of a Cleome-like morphology with open flowers and spreading sepals, a more cylindrical calyx (like Thelypodiopsis). This type of calyx morphology may have facilitated the independent evolution of an urceolate (streptanthoid) calyx in multiple lineages of the Thelypodieae.
1 - University of San Diego, Department of Biology, 5998 Alcala Park, San Diego, California, 92110-2492, USA
Presentation Type: Paper
Location: Cottonwood A (Snowbird Center)
Date: Tuesday, August 3rd, 2004
Time: 4:30 PM