Origins and evolution of cinnamon and camphor: A phylogenetic and historical biogeographical analysis of the Cinnamomum group (Lauraceae)

Tropical and subtropical amphi-Pacific disjunction is among the most fascinating distribution patterns, but received little attention. Here we use the fossil-rich Cinnamomum group, a primarily tropical and sub-tropical Asian lineage with some species distributed in Neotropics, Australasia and Africa to shed light upon this disjunction pattern. Phylogenetic and biogeographic analyses were carried out using sequences of three nuclear loci from 94 Cinnamomum group and 13 outgroup samples. Results show that although there are three clades within a monophyletic Cinnamomum group, Cinnamomum and previously recognized subdivisions within this genus were all rejected as natural groups. The Cinnamomum group appears to have originated in the widespread boreotropical paleoflora of Laurasia during the early Eocene (ca. 55 Ma). The formation and breakup of the boreotropics seems to have then played a key role in the formation of intercontinental disjunctions within the Cinnamomum group. The first cooling interval (50–48 Ma) in the late early Eocene resulted in a floristic discontinuity between Eurasia and North America causing the tropical and subtropical amphi-Pacific disjunction. The second cooling interval in the mid-Eocene (42–38 Ma) resulted in the fragmentation of the boreotropics within Eurasia, leading to an African–Asian disjunction. Multiple dispersal events from North into South America occurred from the early Eocene to late Miocene and a single migration event from Asia into Australia appears to have occurred in the early Miocene.