Dynamics of mixed-ploidy populations under demographic and environmental stochasticities

The population dynamics of autopolyploids – organisms with more than two genome copies of a single species – and their diploid progenitors have been extensively studied. The acquisition of multiple genome copies is heavily influenced by stochasticity, which strongly suggests the efficacy of a probabilistic approach to examine the long-term dynamics of a population with multiple cytotypes. Yet, our current understanding of the dynamics of autopolyploid populations has not incorporated stochastic population dynamics and coexistence theory. To investigate the factors contributing to the probability and stability of coexisting cytotypes, we designed a new population dynamics model that incorporates demographic and environmental stochasticities to simulate the formation, establishment, and persistence of diploids, triploids, and autotetraploids in the face of gene flow among cytotypes. Contrary to previous theoretical research, increased selfing rates and pronounced reproductive isolation promote coexistence of multiple cytotypes. In stressful environments and with strong competitive effects among cytotypes, these dynamics are more complex; our stochastic modeling approach reveals the resulting intricacies that give autotetraploids competitive advantage over their diploid progenitors. Our work is fundamental to a better understanding of the dynamics of coexistence of multiple cytotypes.

Methods
All simulations were generated and analyzed with code provided in this repository.