Dispersal across Wallace's Line: A case study in Endiandra.

Area of Science:

• Paleotropical biogeography
• Plant evolutionary history
• Phylogenomics

Background:

• Floristic exchange between Oceania and tropical Asia is asymmetrical, with rare northward dispersal from Oceania.
• The genus Endiandra (Lauraceae) offers insights into paleotropical biogeography due to its distribution and species richness in Oceania.

Purpose of the Study:

• To investigate the biogeographic history of the genus Endiandra.
• To understand the dispersal patterns between tropical Asia and Oceania.

Main Methods:

• Sequenced plastid genomes (plastomes) of 69 Endiandra species using herbariomic (genome skimming) approach.
• Reconstructed a phylogenomic tree, estimated divergence times, and analyzed ancestral areas.

Main Results:

• Endiandra was found to be a paraphyletic group, with two Australian Beilschmiedia species nested within it.
• The genus originated in Oceania approximately 51.21 million years ago (stem age) and 45.69 million years ago (crown age).
• Multiple independent dispersal events across Wallace's Line shaped the modern distribution of Endiandra.

Conclusions:

• Neogene geological and environmental changes likely facilitated Endiandra dispersal.
• The dispersal patterns of Endiandra are more complex than the established "Dacrycarpus pattern".
• This study enhances understanding of paleotropical plant biogeographic history.