BOGLER, DAVID J.1,2*, ALEXANDRA MARRACCINI1, and JAVIER FRANCISCO-ORTEGA1,2. 1Fairchild Tropical Garden, Research Center, 11935 Old Cutler Road, Miami FL 33156; 2Florida International University, University Park Campus, Miami, FL 33199. - Molecular Systematic Studies of Cycads (Cycadales): initial results based on chloroplast DNA gene spacers, ITS rDNA sequences, and DNA fingerprinting.
Cycads are an ancient group of gymnosperms that were abundant and
widely distributed during the Mesozoic, but are now largely confined
to isolated tropical and subtropical regions. Many cycads are
currently threatened with extinction and there is an urgent need for
more information about their taxonomy and genetics. Extensive
molecular studies of cycads were initiated at the molecular
systematics laboratory set up in collaboration with Florida
International University, utilizing the world renowned cycad
collections at Fairchild Tropical Garden and the Montgomery Botanical
Center. The 11-12 genera of cycads currently recognized are thought to
comprise a monophyletic group, classified as a single order, the
Cycadales, which is divided up into three or four families. Analysis
of morphological characters could not fully resolve all the genera. We
studied cycad phylogeny using a variety chloroplast genes and spacers
(trnL intron, trnS-trnG, psbB-psbF, atpB-rbcL) and nuclear regions
(ITS). The results of this study are presented and assessed with
reference to previous phylogenetic analyses and classification schemes
based on morphology and anatomy. Cycas is the most divergent
genus, followed by Dioon, which is also isolated from the other
genera and contains two major clades. Stangeria appears to be
related to Ceratozamia, Zamia, and Microcycas.
Lepidozamia appears to be more closely related to
Encephalartos in Africa than to Macrozamia. Sequence
variation among the species of Ceratozamia is especially low. DNA
fingerprinting studies were also initiated with Microcycas to
try and find molecular markers for sex determination of seedlings and
markers for future conservation genetics projects.
Key words: cycadales, cycads, DNA, gymnosperms, phylogeny, sequencing