CYCAD PHYLOGENETICS

Cycads are a small but iconic Paleozoic lineage that first appeared in the fossil record about 320 million years ago (Ma), during the Carboniferous, and are one of a handful of seed plant lineages to have persisted through the Mesozoic. Cycad diversity, however, was greatly decreased by extinctions through the Mesozoic; living cycads are now distributed among ten genera, but at least twice as many fossil genera are known. For this reason, reconstructing phylogenetic relationships for cycads using genetic data is akin to putting together a jigsaw puzzle without all the pieces. It is easy to make errors and the completed puzzle will have holes. Similarly, molecular phylogenies may be erroneous and they give an incomplete picture of the evolutionary history of cycads. To address this issue and we are using analyses that integrate both fossil and molecular data.