A library of ancient life
In the subtropical Hoshitate-ura mangrove forest on Iriomote Island, layers of mud hold a genetic library of past ecosystems. Scientists use a technique called sedimentary ancient DNA (sedaDNA) analysis to read this library. By drilling into the sediment and extracting cores, they access a vertical timeline where the deepest layers are the oldest. Preserved within this mud are fragments of DNA from plants and animals that lived thousands of years ago.
This method provides a detailed record of local vegetation, often with greater taxonomic resolution than traditional analysis of pollen or microfossils. In the Iriomote study, researchers could identify specific plant species that populated the area through different eras. The DNA fragments, often less than 100 base pairs long, are extracted, amplified, and sequenced, allowing scientists to reconstruct the plant community composition of the past. This genetic record offers direct evidence of how the local environment responded to large-scale climatic shifts over millennia.