Factors promoting polyploid persistence and diversification and limiting diploid speciation during the K-Pg interlude

Area of Science:

• Evolutionary Biology
• Paleobotany
• Genetics

Background:

• The Cretaceous-Paleogene (K-Pg) extinction event caused significant biodiversity loss.
• Polyploidization, the increase in chromosome number, is a key evolutionary process in plants.
• Previous explanations for post-K-Pg polyploid increase focused on polyploid adaptive traits and hybridization.

Purpose of the Study:

• To propose a novel hypothesis for the surge in polyploidization after the K-Pg mass extinction.
• To investigate the role of diploid species decline in facilitating polyploid establishment and diversification.
• To explore the contribution of gene pool augmentation and multiple origins to polyploid success.

Main Methods:

• Comparative analysis of plant speciation rates before and after the K-Pg boundary.
• Modeling of polyploid establishment and diversification dynamics.
• Review of genetic mechanisms contributing to polyploid persistence.

Main Results:

• The K-Pg extinction created a 'diploid trough,' reducing diploid speciation rates.
• The decline of diploid species opened ecological niches for polyploid colonization.
• Polyploid gene pool augmentation and recurrent origins facilitated diversification and persistence.

Conclusions:

• The demise of diploids was a crucial factor enabling the post-K-Pg polyploid radiation.
• Polyploid success was driven by their ability to incorporate genetic variation from related diploid and polyploid lineages.
• The majority of newly formed polyploids (neopolyploids) were likely autopolyploids.