Behavioural vs. physiological adaptation: which contributes more to the evolution of complex traits in a warming climate?

The article investigates the relative contributions of behavioural and physiological adaptations to the evolution of complex traits in species with temperature-dependent sex determination (TSD) under climate warming. Using individual-based simulation models, it compares the evolutionary responses of pivotal temperature (the physiological threshold producing equal sex ratios) and maternal nesting behaviour (a behavioural trait influencing nest temperature) to rising temperatures. Results indicate that pivotal temperature evolves more readily to correct sex ratio biases, but nesting behaviour plays a significant adaptive role when offspring survival depends on nest temperature. Additionally, behavioural plasticity in nesting reduces selective pressure on both traits, demonstrating that plasticity and multiple selective pressures shape the coevolution of behavioural and physiological traits in changing environments. These findings highlight the complex interplay between behaviour and physiology in adaptation, with implications for understanding evolutionary responses in TSD and other temperature-sensitive sex determination systems.