Genes and Behaviour

Behaviour is the response of an animal to stimuli in its internal or external environment, ranging from simple reflexive behaviours to those that are more complex and goal directed, such as foraging, finding a mate, or engaging in aggressive interactions. However, even reflexive behaviours can be modified by experience. For example, in the zebrafish, Danio rerio, the decision to escape or swim is influenced by social status, achieved through a shift in the excitability of neural circuits (Miller et al. 2017). Therefore, a behavioural act requires an individual not only to process sensory information and respond with motor output, but also to integrate its current internal motivational state and memory of past experiences (Bendesky and Bargmann 2011; O’Connell and Hofmann 2011). As such, the genes that affect behaviour can act to influence many different layers of the nervous system, ranging from sensory perception to the connectivity and modulation of neural circuits (Marder 2012; McGrath 2013). This feature of behaviour, the ability to be modified at many different levels, may contribute to the high evolvability of behavioural traits (Blomberg et al. 2003). To gain an understanding of how animal behaviour evolves requires an integrative approach that examines how behavioural traits are inherited and also characterizes the genetic variants underlying behaviour and their specific effects on neural processing. In this chapter, we present a current understanding of the relationship between genes (of large effect) and behaviour. We first outline how most phenotypic traits, including behaviour, are controlled by many variants of small effect (see also Chapters 1 and 2). We then describe several well-studied examples of single genes that mediate behaviour, as well as ‘supergenes’ that can control behavioural divergence within species. Next, we discuss how certain classes of genes may be more likely to influence the evolution of behaviour. Finally, we consider whether the genetic architecture of behavioural traits is unique in relation to other phenotypic traits. We conclude the chapter by suggesting that an integrative approach to the study of genes and behaviour will lend the most insight into the forces underlying behavioural and genetic diversity.