Iliamna is a temperate North American mallow with eight species, seven of which are classified as rare or endangered. They occupy a range of habitats from streamsides at high elevations to arid hillsides. Cytological and morphological evidence has indicated a close relationship between Iliamna Greene, Malacothamnus Greene, and Phymosia Hamilton to form the Malacothamnus alliance. Malacothamnus is located in California and northern Baja California with an additional species in Chile. Phymosia is found in the Bahamas, southern Mexico, and Guatemala. In habit, species in Iliamna are herbaceous to small shrubs, Malacothamnus shrubs, and Phymosia small trees. All are distinctive in their non-reticulate dehiscent fruits and have showy flowers. Much hybridization has been reported within Malacothamnus and is suspected to occur in Iliamna. The internal transcribed spacer (ITS) of nuclear ribosomal DNA was used to develop a phylogeny for the Malacothamnus alliance. Parsimony was used to develop a phylogenetic tree by random stepwise addition with 100 replicates. Robustness of the phylogeny was tested using decay, bootstrap, and jackknife analyses. The results indicate that Iliamna is paraphyletic and closely allied to Malacothamnus. The phylogeny and biogeographic history of the Malacothmnus alliance will be discussed.

Key words: Iliamna, ITS, Malacothamnus, Malvaceae, Phymosia