Polyploidy: a factor in the evolution of Dicerandra Benth. (Labiatae)

Abstract

Chromosome counts are reported for the first time in Dicerandra Benth. (Labiatae), a genus endemic to the south-eastern United States. Representative taxa are tetraploid (n = 16) and hexaploid (n = 24). Diploids were not found. The systematic, phytogeographic and conservation implications of polyploidy in this genus are discussed. The monophyletic nature of the genus is upheld by the discovery that both sections have a presumed base number of x = 8. Hexaploidy has apparently evolved independently in all branches of sect. Dicerandra, but not in sect. Lecontea.