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Molecular Systematic Studies in Cycads: Evidence from trnL Intron and ITS2 rDNA Sequences
David J. Bogler and Javier Francisco-Ortega
Vol. 70, No. 2 (Apr. - Jun., 2004), pp. 260-273
Stable URL: http://www.jstor.org/stable/4354478
Page Count: 14
You can always find the topics here!Topics: Genera, Introns, Biological taxonomies, Systematics, Botanical gardens, Phylogeny, Taxa, Sequencing, Tropical regions, Parsimony
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The results of a pilot DNA sequencing study of cycads conducted at the new molecular systematics laboratory at Fairchild Tropical Garden are presented and assessed with reference to previous phylogenetic analyses and classification schemes based on morphology and anatomy. Two DNA regions were sequenced and analyzed for variation, an intron in the trnL gene in the chloroplast genome (trnL intron) and the internal transcribed spacer region between the 5.8S and 26S ribosomal DNA subunits (ITS2). The trnL intron proved to be relatively conservative among cycad genera, while the ITS2 region contained higher levels of variation. Parsimony analysis of the sequences suggests a number of relationships, some of which were inferred by previous morphological studies, some of which are new. The sequences of Cycas are the most divergent among cycads, suggesting the longest isolation. Dioon is relatively isolated from the other genera and contains two major clades. Stangeria does not appear closely related to Bowenia but does seem to have a weak affinity with Zamia and Microcycas. Lepidozamia is more closely related to Encephalartos than to Macrozamia. Sequence variation among the species of Ceratozamia is low. Microcycas and Zamia are closely related.
Botanical Review © 2004 New York Botanical Garden Press