The Cinnamomum group is a subset of the tribe Cinnamomeae (Lauraceae) ranging from tropical and subtropical Asia, Australia and Pacific Islands, to tropical America and Africa. Though numerous fossil records should make the Cinnamomum group a desired target to explore the origins of its amphi-Pacific disjunction pattern, the majority of the fossils attributed to Cinnamomum is based purely on superficial similarities of venation features and are not conclusive. Previous studies have revealed that cpDNA makers are of limited use for reconstructing phylogenetic relationships in Lauraceae.

Prof. LI Jie’s team of Xishuangbanna Tropical Botanical Garden (XTBG) and their international collaborators selected three nuclear markers, ITS and two low-copy nuclear genes (LEAFY and RPB2), to resolve phylogenetic relationships within the Cinnamomum group along with a significant increase in taxon sampling. They aimed to reconstruct phylogenetic relationships within the Cinnamomum group and elucidate if the group, the genus Cinnamomum and previously recognized subdivisions within it are monophyletic. They also wanted to explore the biogeographic history of the Cinnamomum group and elucidate the origin and nature of its amphi-Pacific and other disjunctions, including the tropical North and South American disjunction, the African–Asian disjunction and the disjunction between Asia and Australia.

The phylogenetic analyses showed that neither the genus Cinnamomum nor sections Camphora and Cinnamomum were supported as monophyletic. Molecular dating and biogeographic reconstructions suggested that the Cinnamomumg roup arose in the early Eocene of Laurasia, radiating during the warmest period of the Cenozoic accompanied by the expansion of a boreotropical paleoflora in high latitudes of the Northern Hemisphere. The contraction and southward retreats to lower latitudes during the cooling intervals of the later Eocene and onwards caused the intercontinental disjunctions seen in extant Cinnamomum group species. Moreover, long distance dispersal dominated the spread into South America and Australia.

The study entitled “Origins and evolution of cinnamon and camphor: A phylogenetic and historical biogeographical analysis of the Cinnamomum group (Lauraceae)” has been published online in Molecular Phylogenetics and Evolution.