How evolution draws trade-offs

Recent empirical evidence suggest that trade-off shapes can evolve, challenging the classical image of their high entrenchment. Here we model the evolution of the physiological mechanism that controls the allocation of a resource to two traits, by mutating the expression and the conformation of its constitutive hormones and receptors. We show that trade-off shapes do indeed evolve in this model through the combined action of genetic drift and selection, such that their evolutionarily expected curvature and length depend on context. In particular, a trade-offs shape should depend on the cost associated with the resource storage, itself depending on the traded resource and on the ecological context. Despite this convergence at the phenotypic level, we show that a variety of physiological mechanisms may evolve in similar simulations, suggesting redundancy at the genetic level. This model should provide a useful frame-work to interpret and link the overly complex observations of evolutionary endocrinology and evo-lutionary ecology.