A new species of Streptanthus (Brassicaceae) from the North Coast Range of California (U.S.A.)

Streptanthus callizoi R. O’Donnell is a newly described annual endemic species growing in the serpentine soils on Snow Mountain (near Hopland) in Mendocino County, California. The type locality is a serpentine barren, southwest of Hopland along County Road 110 near the summit of Snow Mountain. Previous collections of this taxon at the type locality had been determined as Streptanthus barbiger Greene or S. batrachopus J.L. Morrison. The new species exhibits several character states that distinguish it from S. barbiger: basal rosette, auriculate and non-auriculate cauline leaf bases, small stature (usually < 30 cm), and low branching habit. Several character states distinguish it from S. batrachopus: basal rosette and possession of both auriculate and non-auriculate cauline leaf bases. This rare serpentine endemic merits recognition as a species of conservation concern.