Phylogeny and biogeography of Caryodaphnopsis (Lauraceae) inferred from low-copy nuclear gene and ITS sequences

Caryodaphnopsis is a small genus of the Lauraceae. It contains 16 known species with a disjunct tropical amphi-Pacific distribution; 8 species in tropical Asia and 8 species in tropical America. In the present study, RPB2, LEAFY and ITS sequences of 9 Caryodaphnopsis species and 22 other Lauraceae species were analyzed with maximum parsimony and Bayesian inference. Divergence time estimation employed the Bayesian Markov chain Monte Carlo method under a relaxed clock. Ancestral area reconstructions were conducted by using both the statistical dispersal-vicariance analysis and likelihood approach under the dispersal-extinction-cladogenesis model. Based on the results of the phylogenetic analyses, the monophyly of Caryodaphnopsis is strongly supported. Asian and American Caryodaphnopsis species form two well-supported monophyletic clades, respectively. Independent lineages for Caryodaphnopsis, Neocinnamomum and Cassytha are also suggested. According to the divergence time estimations and ancestral area reconstructions, we suggest that Caryodaphnopsis originated in Late Cretaceous Laurasia and its amphi-Pacific disjunction results from the disruption of ancestral boreotropical lineages between Eurasia and North America during the first cooling period of the Eocene.