Effects of phenotypic plasticity on diversification rates and adaptive evolution in simulated environments with different climatic and cost contexts

Phenotypic plasticity can either hinder or facilitate genetic evolution, thus affecting macroevolution. However, the mechanisms and associations of phenotypic plasticity with biodiversity patterns remain unresolved. We investigated the effect of phenotypic plasticity on adaptive evolution in the context of climatic changes and plasticity costs, specifically examining the rates of trait evolution, speciation, extinction, and diversification. We employed an eco-evolutionary agent-based model, incorporating body temperature as a plastic trait that dynamically responds to fluctuations in environmental temperature. In all simulated scenarios, we found that an increase in plasticity led to a decrease in extinction and trait evolution rates. Speciation rates exhibited a non-linear relationship with plasticity, characterized by an asymmetric U-shaped curve. This intricate speciation pattern likely arises from the interplay of two conflicting forces: (1) low extinction rates foster larger population and range sizes, thereby augmenting the potential for speciation; (2) reduced trait evolution, stemming from stable selection, enhances population homogenization and connectivity, consequently inhibiting speciation. Still, overall diversification tends to increase with plasticity. In sum, our simulation unveils potential mechanisms through which phenotypic plasticity could affect macroevolution – specifically, our results support the hypothesis that plasticity should promote diversification, mainly by reducing extinction, while at the same time reducing the rate of change in the plastic trait.