A stable phylogeny for the cycads

The cycads (order Cycadales) are an ancient order of gymnosperms comprising ten genera and 331 species found in all tropical regions of the earth. Using sequences of five single copy nuclear genes, Salas-Leiva et al. resolve a well-supported phylogeny for the group that is consistent across several methods of analysis. The phylogenetic tree robustly supports a close relationship between the South African monotypic genus Stangeria and the American genera Zamia and Microcycas. Biogeographic analysis suggests that massive extinction events eliminated broader distributions for the ancestors of extant cycads, whose radiation dates to no more than 12 million years ago.