An overview of the evolutionary causes and consequences of behavioural plasticity

I outline how understanding the mechanism of behavioural plasticity is important for predicting how organisms will respond to rapidly changing and novel environments. I define two major forms of behavioural plasticity: developmental and activational. Developmental plasticity refers to the capacity of a genotype to adopt different developmental trajectories in different environments. Activational plasticity refers to differential activation of an underlying network in different environments such that an individual expresses various phenotypes throughout their lifetime. I suggest that the costs and benefits of these two forms of behavioural plasticity may differ: developmental plasticity is slow, but results in a wider range of more integrated responses. Furthermore, the neural costs associated with activational plasticity may be greater because large neural networks must be maintained past an initial sampling and learning phase. While the benefits of plasticity are realized in variable environments, I argue that fine-grained and coarse-grained variation may differentially select for activational and developmental plasticity, respectively. Because environmental variation experienced by an organism is largely determined by behaviour, developmental plasticity may still evolve in fine-grained environments if niche choice results in coarse-grained 'realized' variation. Behavioural plasticity should impact evolution in novel environments because it increases the chances of survival in these environments. Developmental behavioural plasticity may be particularly important for diversification in novel environments because it can impact not only survival, but also the development of signals and preferences important in mate choice. Future areas of research on behavioural plasticity and rapid environmental change include stress as a mechanism underlying rapid integrated responses and life history perspectives on predicting developmental versus evolutionary responses.