The researchers examined sediment samples from the region in the laboratory and identified the fossils they contained. "We wanted to understand how the diversity of the Indo-Australian Archipelago evolved and persisted in the shallow marines, and what factors were responsible for the disproportionately high diversity in the tropics," says first author Skye Yunshu Tian, who started the study at the University of Hong Kong and completed it in the Department of Paleontology at the University of Bonn.
The researchers found that the archipelago has shown an increase in diversification since the early Miocene (around 20 million years ago). Around 2.6 million years ago, the number of species approached a plateau. There were no major extinction events during the entire study period. "The increase in diversity was primarily driven by the habitat factor, as tectonic collisions in Southeast Asia created extensive areas of shallow marine habitats," says Skye Yunshu Tian.
Around 14 million years ago, thermal stress moderated for the Indo-Australian Archipelago. "This was crucial for the development of the hotspot, as excessively high tropical temperatures in warm climate zones during the Eocene and early Miocene hindered the increase in diversity," reports the scientist from the University of Bonn. This could change in the future: "Our paleobiological results suggest that we could quickly lose the fantastic diversity of the tropical hotspot if the ongoing anthropogenic warming intensifies."
