Abstract: How an organism develops and the timing of developmental events are often contingent on the organism's environment. These responses, known as phenotypic plasticity, are frequently adaptive since they allow organisms to maintain high fitness across a wide range of ecological conditions. However, we know little about the molecular mechanisms through which the complex gene regulatory networks governing these responses evolve as species expand their ranges, colonize new areas, or become domesticated. Determining the genetic basis for this ecological diversity is an important goal because this knowledge can indicate what genetic properties and processes facilitate or constrain the evolution of plasticity and whether evolutionary responses to future environmental change are predictable.