Karyotype polymorphism in the cycad Zamia loddigesii (Zamiaceae) of the Yucatan Peninsula, Mexico

Abstract

The cycad Zamia loddigesii Miq. forms a morphologically variable complex on the Yucatan peninsula, Mexico. Several diploid chromosome numbers have been found in the species: 2n = 17, 24, 25, 26 and 27. Differing karyotypes and chromosome numbers were found in individuals of the same population and the karyotypes differ widely in numbers of metacentric and telocentric chromosomes present Centrometric fission as well as pericentric inversions and unequal translocations are suggested to be the probable mechanisms for this karyotype variation. There appears to be a correlation between high chromosome number and increasing dryness of the habitats. Coupled with the strongly asymmetrical karyotypes, this suggests that karyotype evolution in Z. loddigesii is recent. (C) 1996 The Linnean Society of London.