Roldana is centered in the mountains of Mexico and Central America and includes some 48 recognized species. The species are notably imprecise, which has caused a complicated taxonomic history. The taxonomic characters vary both within and among species, however, the micro-morphological characters that distinguish Roldana appear to be reliable and consistent. Roldana species are particularly abundant in the Trans-Mexican Volacanic Belt of south central Mexico and the highlands of Guatemala and adjacent regions. In those areas, the species are notably intergradant, but away from those areas, the species boundries are evidently more distinct. The techniques of cluster analysis are used to circumscribe species and produce a dendrogram for the entire genus. The relationships shown by this analysis are discussed in the context of distributions and geohistorical events.

Key words: Roldana, Senecioneae