Simulated evolution of phenotypic plasticity in a functional-structural plant root model

We aimed to (i) develop a new computational functional-structural plant root model (FSPM) able to represent a wide range of realistic root system structures and growth strategies with varying levels of phenotypic plasticity while being flexible and efficient enough to facilitate our longer term objective of simulating plant populations or communities interacting and evolving over many generations in different conditions and (ii) use this model to study the evolution of root architecture and plasticity in environments with different levels of soil heterogeneity and rainfall frequency. A model was designed to meet the requirements above. We successfully tested the new model by using it together with an evolutionary algorithm to simulate the evolution of populations of plants with asexual reproduction growing independently. Our model was able to represent realistic root system structures and growth strategies while being flexible and efficient enough to simulate plant populations or communities interacting and evolving over many generations in different conditions. Over evolutionary generations, structural root growth strategies developed and overall fitness (measured as shoot biomass) improved. Different strategies evolved in different evolutionary runs and in different conditions. Evolution clearly selected for root branching plasticity in response to increased local soil water content, indicating that this plasticity confers fitness benefits due to increased water uptake. We conclude that dynamic evolutionary FSPMs have the potential to help us understand the eco-evolutionary costs and benefits of different functional-structural growth strategies. Spatial and temporal heterogeneity in water availability causes the evolution of contrasting root architectures, with different levels of plasticity.