The present concentration of species of Melampodium is in western Mexico, an area of considerable habitat (vegetational) diversity, where the Sierra Madre Occidental, the Sierra Madre del Sur, The Balsas Depression, and the Mexican Transvolcanic Belt converge. Ancestral area reconstruction infers this region as ancestral for the genus. Similarly, results of ancestral habitat reconstruction indicate that pine-oak forests are the ancestral habitat type. At the northern end of the range of the genus, the white-rayed complex occupies a large area from Arizona to central Texas, north into Oklahoma and Colorado, and south into Mexico. Earlier hypotheses suggested the origin of this complex on the eastern side of Mexico, followed by migration northward through the low mountains of Nuevo León and Coahuila and subsequent northward expansion. Comprehensive populational studies in the white-rayed complex with AFLPs and chloroplast haplotypes have revealed instead an origin in northwestern Mexico along the Sierra Madre Occidental and into Arizona, followed by eastward migration and differentiation.