Chromosome numbers in Ferocactus (Cactaceae: Cactoideae)

Abstract

Meiotic and mitotic chromosome numbers were determined for 14 taxa of Ferocactus. Chromosome numbers are reported for the first time for seven species, including two varieties of F. peninsulae, and chromosome counts were confirmed for an additional six species. All taxa investigated were diploid and have a basic chromosome number of x = 11. Within the Cactaceae, Ferocactus appear to have the largest chromosomes. Meiotic figures in Baja Californian and Mexican mainland species failed to document hybridization at least for those populations investigated. The morphological homogeneity of chromosomes and the apparently consistent diploid condition throughout the genus suggest that chromosome evolution in Ferocactus is taking place at the molecular level.