Plants with double genomes might have had a better chance to survive the Cretaceous–Tertiary extinction event

TLDR

Ancient and recent whole‑genome duplications are common in flowering plants, and polyploid species are thought to have greater adaptability, which may have helped them survive the Cretaceous‑Tertiary mass extinction that eliminated ~60 % of plant species. We propose that polyploidization may have contributed to the survival and propagation of several plant lineages during or following the KT extinction event. We dated recent duplication events using penalized‑likelihood phylogenetic inference of paralogous genes and argue that polyploidy’s gene‑expression changes and expanded genetic repertoire could confer adaptive advantages. We show that a majority of these independent genome duplications are clustered in time and seem to coincide with the Cretaceous‑Tertiary (KT) boundary.

Abstract

Most flowering plants have been shown to be ancient polyploids that have undergone one or more whole genome duplications early in their evolution. Furthermore, many different plant lineages seem to have experienced an additional, more recent genome duplication. Starting from paralogous genes lying in duplicated segments or identified in large expressed sequence tag collections, we dated these youngest duplication events through penalized likelihood phylogenetic tree inference. We show that a majority of these independent genome duplications are clustered in time and seem to coincide with the Cretaceous-Tertiary (KT) boundary. The KT extinction event is the most recent mass extinction caused by one or more catastrophic events such as a massive asteroid impact and/or increased volcanic activity. These events are believed to have generated global wildfires and dust clouds that cut off sunlight during long periods of time resulting in the extinction of approximately 60% of plant species, as well as a majority of animals, including dinosaurs. Recent studies suggest that polyploid species can have a higher adaptability and increased tolerance to different environmental conditions. We propose that polyploidization may have contributed to the survival and propagation of several plant lineages during or following the KT extinction event. Due to advantages such as altered gene expression leading to hybrid vigor and an increased set of genes and alleles available for selection, polyploid plants might have been better able to adapt to the drastically changed environment 65 million years ago.