Variation in the Mexican cycadDioon edule (Zamiaceae)

Abstract

The Mexican cycadDioon edule with its two varieties,edule andangustifolium, range from the states of Tamaulipas and Nuevo León in the north to the state of Veracruz in the south. The varietyangustifolium is restricted to the northern portions of the range, while the varietyedule is from the southernmost distribution in central Veracruz. Between the two varieties ofDioon edule there are a number of disjunct colonies that exhibit variations that are undoubtedly the result of an extended period of genetic isolation. These colonies display variation in the maximum size of their stems, morphology and color of leaves and leaflets, distinctions in both male and female cones, color of the sarcotesta, and size and shape of the sclerotesta. These differences are maintained even when specimens are grown in cultivation under identical conditions. Critical investigations of these colonies may ultimately disclose the need for additional species descriptions.