Baccharis Malibuensis (Asteraceae): A New Species from the Santa Monica Mountains, California

Baccharis malibuensis is described from the Malibu Lake region of the Santa Monica Mountains, Los Angeles County, California. It is closely related to Baccharis plummerae subsp. plummerae but differs in having narrow, subentire, typically conduplicate, sparsely villous to mostly glabrous leaves with glands occurring in depressions on the adaxial surface, more cylindrical inflorescences, and a distribution in open chaparral vegetation. The new taxon shares some characteristics with B. plummerae subsp. glabrata of northwestern San Luis Obispo County, e.g., smaller leaves, reduced vestiture, and occurrence in scrub habitat, but the two taxa appear to have developed independently from B. p. subsp. plummerae. As the new taxon is morphologically recognizable, occurs in a different habitat, and exhibits no introgression with subsp. plummerae, it is recognized as a distinct species.