Mahonia

Mahonia is a genus of approximately 70 species of evergreen shrubs and rarely small trees in the family Berberidaceae, native to eastern Asia, the Himalaya, North and Central America. They are closely related to the genus Berberis and botanists disagree on whether to recognize a separate Mahonia. Many botanists prefer to classify Mahonia as a part of Berberis because several species in both genera are able to hybridize, and because there are no consistent morphological differences between the two groups other than the leaf pinnation (Berberis sensu stricto appear to have simple leaves, but these are in reality compound with a single leaflet and are termed "unifoliolate"; additionally their branched spines are modified compound leaves). However, a recent DNA-based phylogenetic study retains the two separate genera, by clarifying that unifoliolate-leaved Berberis s.s. is derived from within a paraphyletic group of shrubs bearing imparipinnate evergreen leaves, which the paper then divides into three genera: Mahonia, Alloberberis (formerly Mahonia section Horridae), and Moranothamnus (formerly Berberis claireae); it confirms that a broadly-circumscribed Berberis (that is, including Mahonia, Alloberberis, and Moranothamnus) is monophyletic.