A PHYLOGENETIC ANALYSIS OF AMERICAN ZAMIACEAE (CYCADALES) USING CHLOROPLAST DNA RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISMS

A phylogenetic analysis of American cycad genera, all belonging to the family Zamiaceae, was attempted using chloroplast DNA restriction fragment polymorphisms. Ceratozamia mexicana Brongn., Chigua restrepoi D. Stevenson, Dioon edule Lindley, Microcycas calocoma (Miq.) A. DC., Zamia fischeri Miq., and Zamia skinneri Warsz. ex A. Dietrich were used as representatives of the genera. Cycas revoluta Thunb., belonging to the family Cycadaceae, was used as an outgroup, following previous morphological works. One hundred and forty-one shared restriction fragments were scored for presence/absence and both Wagner and Dollo parsimony analyses were performed. The single, fully resolved, most parsimonious trees obtained from the analyses were topologically identical and perfectly matched previous morphology-based phylogenetic hypotheses. Statistical evaluation of the data showed a good reliability for the obtained phylogeny. Dioon edule, belonging to a different subfamily and more primitive on morphological grounds, proved to be the most primitive among American cycads as inferred from the molecular data; Chigua restrepoi, never analyzed before on cladistic grounds, was found to be the sister group of the genus Zamia.