XVI International Botanical Congess

The genus Sidalcea (Malvaceae) consists of ca. 25 species distributed in the Southwest U.S., the majority endemic to California. A phylogeny has been constructed using sequences from two regions in the 18-26S nuclear ribosomal DNA: ITS (Internal Transcribed Spacer) and the more variable ETS (External Transcribed Spacer) region. The results contradict the proposed monophyly of the annuals, which show an elevated mutation rate compared to the perennial lineages. Other species groups (e.g., the S. oregana group) which have been noted for high phenotypic plasticity or proposed to hybridize show very low variation in the sequenced regions, a pattern consistent with recent radiation of these taxa from a common ancestor.