Introduction

The end-Cretaceous event (66 Ma) set an ecological catastrophe that reshaped plant communities worldwide. Yet, until recently, the fate of tropical forests following the K/Pg boundary had been largely unknown.



Methods

We quantified plant extinction and ecological change in tropical forests resulting from the end-Cretaceous event using fossil pollen (>50,000 occurrences) that span the Maastrichtian and Paleocene (72–56 Ma), and leaves (>6,000 specimens) from pre- and post-extinction localities in Colombia.



Results

Late Cretaceous (Maastrichtian) rainforests were mixed assemblages of ferns, conifers, and flowering plants, characterized by an open canopy and diverse plant–insect interactions. Insect-feeding behavior, evidenced through feeding-damage, showed high levels of host-plant specificity across communities of insect herbivores. At the K/Pg boundary, plant diversity declined by 45% and did not recover for ~6 million years, setting a long interval of unusual low plant diversity in the Neotropics.

Paleocene forests resembled modern Neotropical rainforests, with a closed canopy, multistratal structure, dominated by angiosperms. These post-extinction forests were ecologically diverse and included coastal rainforests with periodic flooding and inland forests growing in well-drained soils in which legume trees were consistently the most abundant and diverse group of plants. Insect feeding-damage was far more generalized across host plants than in pre-extinction assemblages.



Conclusions

The post-extinction assembly of multistratal, closed canopies, and the establishment of legumes as major biomass producers, hints towards fundamental changes in carbon fixation, evapotranspiration, and nutrient cycling in tropical environments. The extinction at the end-Cretaceous ultimately enabled the assembly of modern ecosystems and established the initial stages in the evolution of Neotropical rainforests.