Phylogeny and Divergence Time Estimation in Illicium with Implications for New World Biogeography

Illiciaceae comprise the single genus, Illicium, and approximately 30-40 species distributed in southern and eastern Asia, the southeastern United States, Mexico, and the Greater Antilles. On the basis of perianth morphology, current taxonomic treatments recognize two sections that do not correspond to geographic distributions. A recent phylogenetic study using ITS sequences found strong support for separate Old and New World clades, but did not include all New World species. We elaborate on this previous study by including all known New World species of Illicium, as well as additional Asian species, using ITS and the plastid loci trnL, the trnL-F spacer, and trnG. We estimated divergence times within Illicium using penalized likelihood and multiple fossil calibration points. Our results support separate New and Old World clades, and we re-circumscribe current sectional groupings based on these data. The Illicium crown group appears to have arisen during the Cretaceous, with New World extant taxa diversifying as recently as the late Miocene or early Pliocene. These dates are consistent with recent fossil evidence and molecular estimates for minimum ages of the angiosperms, and for timing of diversification events in other ancient groups, such as Nymphaeales and Chloranthaceae.