The eight species of Iliamna have a taxonomically complex history. Since its conception in 1906, the genus was not recognized for some time, several species were placed into other genera, and the status of a few species was questioned. Six species are located in western North America and two are found isolated to the east. Species in Iliamna are very similar morphologically with only a few characters distinguishing several as separate entities. The need for systematic study became apparent since all but one species is considered rare or endangered and the differentiation between two endangered species, I. corei and I. remota, was unclear in a previous study using RAPDs. Of the western species, four overlap in distribution (I. crandalii, I. grandiflora, I. longisepala, and I. rivularis) and their recognition as independent species has been questioned. The focus of this study was to develop a phylogeny for Iliamna using sequences from the Internal Transcribed Spacer Region in order to determine the biogeographical and evolutionary history. Cladistic analyses were performed and the resulting phylogeny is presented. Iliamna forms a well-supported clade distinct from related genera and is monophyletic. Three well-supported groups are formed. One contains representatives from the Pacific Northwest and forms the base of the genus. Another contains all of the remaining species with the third clade nested therein. This last clade contains the two eastern species, I. corei and I. remota, but there is little to support the divergence of these taxa as distinct species. Unfortunately, there is not enough variability in the ITS region to separate the western species I. crandalii, I. grandiflora, I. longisepala, and I. rivularis as distinct species either. The ITS data does provide information that brings new insight to the origination of the genus and its distribution, yet further work remains to resolve the uncertainties.

Key words: Iliamna, internal transcribed spacer (ITS), Malvaceae, phylogeny