The timing and ecological consequences of the late Pleistocene megafaunal declines on the Isthmus of Panama: Implications for trophic rewilding

The timing and ecological consequences of Late Quaternary megafaunal extinctions in Central America remain poorly resolved, limiting our understanding of how the Pleistocene megafaunal declines may have influenced past and present ecosystem dynamics and ecological processes. To address this gap, we applied a high-resolution multiproxy palaeoecological approach to reconstruct the Pleistocene megafaunal presence in the Isthmus of Panama. Lake sediment cores from Lake La Yeguada were analysed for spores of coprophilous fungi (SCF) using a multi-genus SCF approach; an analytical advancement that significantly improves the resolution and reliability of megafaunal reconstructions compared to traditional reliance on Sporormiella alone. This multi-genus SCF approach was integrated with fossil pollen and charcoal analyses to establish the first detailed record of megafaunal presence/absence, vegetation dynamics, and fire activity, respectively, spanning the Late Pleistocene to the Holocene in Panama. Our SCF record indicates that megafauna were present in the region from at least 16,600 cal yr BP (calibrated years before present) and underwent three distinct phases of decline around 13,600, 10,000, and 8400 cal yr BP. These declines were followed by recoveries at 11,200, 9000 cal and 7600 cal yr BP, likely caused by changes in megafaunal community compositions. These transitions coincided with shifts in vegetation composition between forest and grasslands, marked by the loss of large-seeded, megafaunal-dispersed plant taxa and increased fire activity, suggesting that megafaunal decline had cascading impacts on ecosystem processes in Panama. Our findings highlight the ecological consequences of megafaunal declines on megafaunal-dispersed and large-seeded plants and suggest that future declines could have implications for vegetation and fire activity. These insights provide a valuable baseline to inform conservation strategies for extant species and offer guidance for future trophic rewilding efforts aimed at restoring ecological functions lost with the extinction of Pleistocene megafauna.