Malacothamnus

Abstract: A new genus, Andeimalva, is described to accommodate four species previously placed in Tarasa and Malacothamnus. The taxonomic placement of the Chilean species M. chilensis in the primarily North American genus has been questioned for nearly 40 years. This species occurs in the Andes of central Chile, unlike the rest of the genus, which is distributed in California, Baja California, and Mexico. Molecular phylogenetic data revealed the strongly supported relationship of Malacothamnus chilensis to the Andean species Tarasa machupicchensis, T. mandonii, and T. spiciformis. The latter species share with M. chilensis the unusual base chromosome number of x = 6, which is not found in other members of Tarasa or other closely related genera (x = 5), or the North American Malacothamnus (x = 17). Considering the phylogenetic and chromosome data, as well as morphology and geography, these four species form a clade that merits generic status and are recognized at generic rank.