In a new study published today in Science, researchers from the Royal Botanic Gardens, Kew (RBG Kew), together with global partners, combine results from two newly discovered prehistoric palm fossils with DNA from global palm collections to gain new insights into the origins of biodiversity in one of the most species-rich places on Earth—the Asian tropical rainforests.
Dr. Benedikt G. Kuhnhäuser, scientist at RBG Kew and lead author of the study, says, “Where does biodiversity come from? It’s a question many generations of biologists have spent their time thinking about. We still understand very little about how plant and animal diversity became so rich in certain areas, such as tropical rainforests, and what causes it to spread as it does. Crucially, if we don’t understand biodiversity, we can’t protect it.
“Our study set out to address this by looking at rattans—the climbing palms predominantly found in tropical Asian rainforests and known for their use in cane furniture. Using DNA sequencing technology to look at the world’s herbarium specimens, including the fantastic palm collections at Kew, alongside newly discovered and incredibly old fossils from the island of New Guinea, we were able to generate estimates on when, where and how rattan palms and their ancestors came into existence.”
Tropical Asia, spanning a distance of 8,000 km with over 20,000 islands, is among the most diverse places on the planet, home to an incredible array of wildlife, including 50,000 plant species and 7,000 vertebrate species (such as birds and mammals). But very little is still known about where this diversity came from and how it spread across the various islands in the region, such as New Guinea, Borneo and the wider Indonesian archipelago.
To understand the origins of tropical Asian biodiversity through time and space, you need data on dispersal and speciation (emergence of new species). Recognizing a clear knowledge gap for this information, the paper’s authors—an international team from the UK, Indonesia, Malaysia, Singapore, U.S. and Denmark, with skills across taxonomy, paleontology and evolution—set out to address this by looking at rattan palms, which are an ideal model group because of their high diversity of around 500 species across the Asian tropics.
A view of the rainforests on the island of Borneo. Although incredibly rich in plant biodiversity, little is known about the origins of this biodiversity across the Asian tropics. Borneo was found to be central in the generation of the modern-day diversity of rattan palms. © Benedikt Kuhnhäuser
Leveraging the world’s herbarium collections (i.e. collections of dried plants), including the extensive palm collections at RBG Kew, the scientists sequenced DNA from hundreds of rattan species to build a tree of life that shows how they are related to each other. The researchers then combined this tree of life with data from the analysis of two 90-million-year-old pollen fossils discovered 1,930 m below ground in New Guinea, which are described as new fossil species in this study.
This incredible dataset made it possible to generate estimates of when modern rattan palms and their ancestors originated, and how they spread and diversified across the Asian tropics. The study authors found that 90% of rattan diversity emerged in the past 30 million years, rapidly spreading from Southeast Asia across the Asian tropics.
The island of Borneo, situated in the heart of the Asian tropics, was found to be of central importance in generating the modern-day diversity of rattan palms and crucial for enabling their spread across the Asian tropics. The island of New Guinea was found to have generated many new species in isolation but to have had limited influence on the diversity of other parts of the Asian tropics, while islands such as Sumatra acted as corridors that enabled the spread of rattan diversity within tropical Asia.
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These findings show that individual islands played very different but equally important roles in generating and enabling the spread of biodiversity, acting together to generate the incredible biodiversity of the Asian tropics that we can see today.
Co-author Jun Ying Lim, Centre for Nature-based Climate Solutions and Department of Biological Sciences, National University of Singapore, Singapore said, “Rattans are some of the most iconic and conspicuous plants in the wet tropical forests of Asia, and it is through them that we highlight how evolution in the Asian tropics is special compared to the other tropical realms.
The rattan palm Calamus sparsiflorus in rainforest on the island of Borneo. © Benedikt Kuhnhäuser
“The vast and complex geographic setting of archipelagic Southeast Asia has probably shaped the diversification for many other plant groups similarly, and we hope that through careful study of more plant groups we will be able to uncover the factors that influence evolution in this rich but threatened part of the world.”
The study’s authors hope that this new research will help to strengthen knowledge of Asian rainforest plant diversity and be used to inform where conservation policy can be implemented and prioritized.
Kuhnhäuser says, “With funding for conservation being limited, vital data such as this can help to make informed decisions on conservation priorities. For example, being able to understand the individual roles that regions have played in the generation and spread of biodiversity is key for identifying the right measures to ensure their protection.”
Co-author Himmah Rustiami, Herbarium Bogoriense, Research Center for Biosystematics and Evolution, National Research and Innovation Agency (BRIN), Cibinong, Bogor, Indonesia, added, “This paper will provide a solid foundation for research on the biogeography and evolution of rattan in tropical Asia, particularly Indonesia.”
More information:
Science (2025). www.science.org/doi/10.1126/science.adp3437
Provided by
Royal Botanic Gardens, Kew
Citation:
DNA and 90 million-year-old pollen fossils reveal new insights into evolution of Asian tropics (2025, March 13)
