Eocene amber fossils reveal how complex trophic interactions shaped tropical rainforest biodiversity

The Eocene Epoch represented a pinnacle in Indian paleobiodiversity, explained by the ESAT (energy-stability-area-time) theory, which links climatic stability and geological time in fostering immense biodiversity. We provide a reconstruction of a middle Eocene tropical ecosystem from an amber biota recovered from the Harudi Formation (∼41.6 ± 0.5 to ∼40.8 ± 0.5 Ma), Umarsar Lignite Mine (ULM), western India. It reveals a highly diverse ecosystem (>800 arthropods of various taxonomic ranks along with 78 genera and 118 species of palynomorphs) thriving in warm and humid conditions (mean temperature ∼25°C; rainfall ∼2,450 mm/year), analogous to modern tropical climates. The findings show that favorable climate, ecological complexity, and India's northward drift facilitated tropical lineage diversification, reinforcing ESAT as a robust explanatory model for deep-time biodiversity patterns. These findings also offer valuable analogs for predicting how biodiversity and functional networks in current tropical forests might respond to ongoing climate change, emphasizing the need to conserve both species and their ecological interactions.