Neutral processes underlying the macro eco-evolutionary dynamics of mixed-ploidy systems.

Area of Science:

• Plant evolutionary biology
• Ecology
• Genetics

Background:

• Polyploidy, the presence of multiple chromosome sets, is crucial in plant evolution, with most flowering plants having polyploid ancestors.
• Newly formed polyploids face challenges like genome shock and reduced fertility when establishing in diploid populations.
• Existing explanations for polyploid success often rely on fitness or niche advantages, but evidence is mixed, and niche overlap is common.

Purpose of the Study:

• To investigate whether neutral evolutionary processes can explain the establishment and persistence of polyploids in mixed-ploidy populations.
• To develop a spatially explicit eco-evolutionary model to simulate polyploid dynamics.
• To provide a theoretical framework for understanding long-term mixed-ploidy population evolution.

Main Methods:

• Development of a neutral, spatially explicit, eco-evolutionary model.
• Simulation of organism assembly in space through iterative processes.
• Analysis of frequency-dependent mating and fertility in simulated populations.
• Comparison of model predictions with empirical data, specifically phylogenomic estimates of species extinctions in Brassicaceae.

Main Results:

• The model demonstrates that neutral processes, specifically spatial self-structuring, can facilitate polyploid establishment.
• Iterative spatial assembly allows sexually reproducing organisms to overcome mating disadvantages and fertility issues.
• The model provides a mechanistic explanation for polyploid persistence without requiring significant fitness or niche differentiation.
• Model outputs align well with observed extinction patterns in the Brassicaceae family.

Conclusions:

• Neutral spatial processes offer a viable mechanism for the establishment and long-term persistence of polyploids.
• This framework challenges the necessity of strong selection-driven advantages for polyploid success.
• The study provides a new theoretical lens for understanding the evolutionary trajectories of mixed-ploidy populations.