Tuesday, June 19, 2007 - 4:55 PM
Ponderosa Pines (Boise Centre on the Grove)

A phylogenetic analysis of Lepidium papilliferum and L. davisii (Brassicaceae) reveal the relations of these rare endemic species

James F. Smith1, Amy J. Stillman1, Steven R. Larson2, Culumber C. Mae2, Ian C. Robertson1, and Stephen J. Novak1. (1) Boise State University, Boise, ID, (2) Utah State University, Logan, UT

Previous phylogenetic analyses of Lepidium included only a few accessions of L. montanum and L. fremontii to represent the western North American species. Two additional species endemic to southwest Idaho have posed both taxonomic and conservation questions regarding their species status. Lepidium papilliferum was originally described as a variety of L. montanum. The plant is restricted to specific edaphic conditions known as slick spots where high clay content creates conditions amenable to L. papilliferum. Like L. papilliferum, L. davisii has specific edaphic requirements and is found in playas, areas similar to slick spots, but larger and with deeper soils. Previous phylogenetic studies have shown that American species of Lepidium are allopolyploids with one genome derived from an African clade and the other from an Asian/European clade. In this study we expanded previous analyses to include both L. papilliferum and L. davisii with several accessions of L. montanum along with published sequences of ITS, cpDNA and PISTILLATA first intron. Our results agree with previous studies in that this group has one genome derived from within an African clade and another from an Asian/European clade. The western North American species form a monophyletic group with L. davisii sister to the remainder of the clade. Within this clade L. papilliferum and L fremontii are each monophyletic and sister to each other, but are imbedded within a paraphyletic L. montanum. These data suggest that greater sampling among populations and subspecies of L. montanum and other Lepidium species will be required.