XVI International Botanical Congess

The phylogenetic relationships within the genus Lasthenia were investigated using sequences of the ITS region. Thirty samples representing 16 of the 17 species of Lasthenia were included in the analysis. The ITS phylogeny suggests several interspecific relationships that are incongruent with relationships previously suggested based on morphological and cytological data. Most sections as currently delineated are polyphyletic. Surprising results include the placement of L. fremontii (sect. Ptilomeris) in section Baeria and the basal position of L. glaberrima (sect. Lasthenia). However, the ITS phylogeny suggests monophyly in section Hologymne and supports a close relationship among populations of L. californica and of L. macrantha (sect. Baeria) and between these species and L. leptalea (Sect. Burrielia).