Fungal proliferation before and after the Cretaceous-Paleogene mass extinction event in North America.

Palynological evidence of postcatastrophe fungal proliferation after global calamities has been found for the Permian-Triassic and Cretaceous-Paleogene (K/Pg) extinction events. However, unlike the globally documented post-Permian fungal bloom, evidence of a post-Cretaceous event has previously been limited to a single site in New Zealand. Our analysis of a K/Pg boundary section from the Denver Basin in Colorado revealed a fungal proliferative spike occurring immediately after the Chicxulub meteorite impact. The discovery of a postimpact fungal bloom in North America corroborates the New Zealand finding and supports the interpretation that this was a global phenomenon. We also identified a prolonged interval of elevated fungal abundance in the Late Cretaceous, dating to approximately 30,000 to 10,000 y before the impact, temporally correlated to a period of climatic cooling at the site and intriguingly coincident with the high-volume Poladpur phase of the Deccan Traps volcanic eruptions. Taken together with reports of fungal expansion following prior global calamities, these findings indicate that fungi can often flourish in the aftermath of ecosystem-level collapse. Given the capacity of fungi to cause disease in both plants and animals, the occurrence of fungal proliferative events has potential implications for the recovery of species surviving global cataclysms.