Phylogeny and Biogeography ofRhus(Anacardiaceae) Based on ITS Sequence Data

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Abstract
Rhus L. (sensu lato) has been considered the largest and most widespread genus in the Anacardiaceae. Controversy has surrounded the delimitation of the genus. Historically, seven segregate genera have been recognized: Actinocheita, Cotinus, Malosma, Melanococca, Metopium, Searsia, and Toxicodendron. These genera, together with Rhus s.str., are commonly referred to as the Rhus complex. Rhus s.str. includes two subgenera, Lobadium (ca. 25 spp.) and Rhus (ca. 10 spp.). Sequences of the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA were employed to examine the monophyly of Rhus s.str. and to provide insight into the phylogenetic and biogeographic history of the genus. The ITS data set indicates that Rhus s.str. is monophyletic. Actinocheita, Cotinus, Malosma, Searsia, and Toxicodendron are distinct from Rhus s.str., although the relationships among these genera of the Rhus complex are not well resolved. Rhus subgenus Rhus is paraphyletic; the monophyletic subgenus Lobadium is nested within it. The ITS data set indicates that, for Rhus, the Madro‐Tertiary floristic element (subgenus Lobadium) had a single origin within the Arcto‐Tertiary floristic element (subgenus Rhus).