REVISION OF THE DIOECIOUS GENUS CHERSODOMA PHIL (SENECIONEAE, ASTERACEAE), INCLUDING A NEW SPECIES AND STATUS CHANGE

A revision of the dioecious genus Chersodoma (Senecioneae, Asteraceae) recognizes nine species, including a new species, C. deltoidea Sagast . & M. O. Dillon, from northern Peru and a status change for a northwe stern Argentine endemic, C. glabriuscula (Cabrera) M. O. Dillon & Saga st. Chersodoma is confined to the Andean Cordillera and is the only di oecious member of the Senecioneae in continental South America. A clad istic analysis of a morphological data set supports the monophyly of t he genus and the recognition of two previously established subgenera. Subgenus Chersodoma contains three species (C. argentina, C. candida, C. jodopappa) with greatest diversity in the semi-arid puna of northwe stern Argentina and adjacent Bolivia and Chile. Subgenus Diclinanthus B. Nord., contains six species (C. antennaria, C. arequipensis, C. del toidea, C. juanisernii, C. glabriuscula, and C. ovopedata) with greate st diversity in Peru. A key to Andean genera of Senecioneae is provide d. A discussion of species relationships and historical biogeography i s presented as suggested by morphological parsimony analysis.