The Rise of Polyploids During Environmental Upheaval

Polyploidy, or whole-genome duplication (WGD), serves as both a significant evolutionary force and a potential evolutionary dead end, occurring extensively across the tree of life, particularly among angiosperms. Despite the prevalence of polyploid organisms, instances of ancient polyploidy are surprisingly rare, presenting a paradox that remains poorly understood. In this study, we constructed a comprehensive genomic dataset of 470 angiosperm species to address this issue. We developed a highly congruent evolutionary timescale and dated 132 ancient WGD events that are non-randomly distributed, revealing a clustering around pivotal periods of environmental upheaval and extinction. Notably, our findings highlight a strong correlation between waves of paleopolyploidization and significant events such as the Middle Miocene Disruption, the Eocene-Oligocene transition (EOT), the Paleocene-Eocene Thermal Maximum (PETM), the Cretaceous-Paleogene (K-Pg) extinction, and different oceanic anoxic (OAE) events, several of which can be linked to extinction events impacting flowering plant genera. By integrating multiple lines of evidence, we propose that polyploid organisms have an increased chance of survival during times of great environmental turmoil, a conclusion with important implications in the context of contemporary climate change and rapid global warming.