The role of behaviour in the establishment of novel traits

It may seem as if behaviour is so plastic that it would not foster the establishment of a genetically determined trait, but under some circumstances, it can greatly influence whether a novel trait, such as a new morphology, spreads in a population. If the behaviours associated with the trait's function already exist, a new variant finds a ready foothold, and selection can act accordingly. Behaviours that are particularly likely to foster novel traits include those that play a role in life history, such as antipredator behaviour, sexual signalling and foraging. Examples of behaviour facilitating novel trait establishment include the spread of a silent mutant in male Pacific field crickets, Teleogryllus oceanicus, and the propensity of juvenile fence lizards to show antipredator behaviours towards attacking fire ants, providing a selective opportunity for the evolution of longer limbs. The genetic or physiological mechanisms behind a behaviour can also influence its establishment; for example, learning may generate selection in favour of conspicuous novel traits faster, and for a wider range of traits, than genetically based sensory biases. Just as changes in behavioural traits over evolutionary time may expose populations of individuals to new adaptive zones, behavioural variation within a population may increase the diversity of environments to which individuals are exposed.