Cladistic analyses of Iris included 18 ingroup taxa from series Californicae and two outgroup taxa from series Sibiricae. The internal transcribed spacers and the 5.8S subunit of 18–26S nuclear ribosomal DNA were sequenced to provide phylogenetic information. An analysis of DNA data resulted in five most parsimonious trees that concurred in part with morphological data. Species groups in series Californicae that have been informally proposed by previous workers were not supported in this study. Two species complexes, I. tenax and I. hartwegii, were not monophyletic as currently delineated. Support for several internally resolved clades is low with DNA data, probably due to high levels of homoplasy along some branches. The overall level of variation and sequence divergence is relatively high compared to other infrageneric plant groups.

Communicating Editor: James F. Smith