Evolution of behavioural phenotypes: influences of ancestry and expression

Behavioural phenotypes are invariably plastic to some degree and are among the most labile of phenotypes. Some are acquired over the course of development in a particular environment (developmental plasticity), but most are elicited by an environmental trigger and are expressed only briefly, but often repeatedly, in the life of an organism (activational plasticity). Thus, individuals can possess the ability to perform a behaviour, but in the absence of the appropriate environmental stimulus, can fail to do so over the course of a lifetime. Rarely is the evolution of behavioural phenotypes explored in the larger context of the evolution of phenotypically plastic traits. Here I argue that the evolution of behavioural phenotypes, regardless of the nature of the plasticity expressed, can be examined in the same way as the evolution of other plastic traits. I first provide a conceptual review of the factors that can influence the evolution of plastic phenotypes and of the ways in which behavioural plasticity can influence the evolution of other aspects of phenotype. Many of the most compelling questions involve contrasting ancestral patterns of plasticity with those in derived populations or species, a particularly challenging problem in the case of phenotypic plasticity. I therefore provide an overview of the ways in which the influence of plasticity upon evolution can be addressed and then provide a review of examples from the literature that offer initial insights into the role of behavioural plasticity in evolution. The questions are exciting, the data limited, and, as I argue in closing, we need creative insights into the ways in which behavioural plasticity has evolved and has in turn influenced the evolution of other aspects of phenotype.

► Behavioural plasticity evolves as does plasticity of other trait types.
► Behaviour thus undergoes genetic accommodation.
►  Behaviour can influence the evolution of other phenotypes.
► Four methods can elucidate the role of behaviour in evolution.
►  Examples are used to illustrate compelling questions in evolution.