Quantitative and molecular genetics of animal personality

Correlated suites of behavior are collectively known as animal personality (Gosling 2001), behavioral syndromes (Sih et al. 2004), behavioral strategies (Benus et al. 1990), or behavioral profi les (Rodgers et al. 1997). Each of these terms, to some extent, describes an emergent phenomenon of the total biases in behavioral reactions an individual expresses compared with other individuals within the same population or species. While there is some debate on terminology (e.g., Réale et al. 2007; Gosling 2008; introduction, this volume), we will use the term animal personality throughout this chapter. Recent evidence suggests an important role for within-population variation in animal personality for our understanding of ecology and evolution, since behavioral variation often covaries with several important indicators of fitness, such as growth, reproduction, and survival (Dingemanse and Réale 2005; Smith and Blumstein 2008; see chapters 3, 7, and 13). In line with several other fields in the life sciences (Pigliucci 2007; Wingfield et al. 2008), a re-emerging theme or emphasis of many studies of animal personality is how selection on correlated suites of traits (as opposed to a singular focus on any one trait in an isolated context) may influence and be influenced by evolutionary and population dynamics (see Van Oers and Mueller 2010). To take one example, predators selecting on individual prey with certain behavioral characteristics can result in particular personality types (i.e., covariance between aggression and boldness) in some populations but not in others, which in threespined stickleback fish (Gasterosteus aculeatus) has been demonstrated in a descriptive way (Dingemanse et al. 2007; Alvarez and Bell 2007; Brydges et al. 2008) as well as in an experimental way (Bell and Sih 2007; see chapter 2). This effect of correlated selection on evolutionary and population dynamics can also be found in human-induced selection on fisheries: fast-growing individuals, which are also the boldest foragers, are most likely to be caught in fishing nets, causing the phenotypic and genotypic behavioral and growth structure of natural fish populations to be altered (Biro and Post 2008). In another example, consistent behavioral differences influence natural selection by influencing settlement patterns in Western bluebirds (Sialia mexicana), where males aggressively compete for territories. Males with higher levels of aggressiveness are more successful in preferred habitats with multiple nesting possibilities per territory (Duckworth 2006b). The physical habitat characteristics of these areas, however, also induce correlated selection on morphology: in preferred areas there was positive selection on longer tarsi and tails where agility was favored, while in less preferred habitats (where agility was also not as important) there was no morphological selection on these physical characteristics (Duckworth 2006a). In short, variation in animal personality represents an important behavioral mechanism that links life-history characteristics to variation in fitness across a wide range of taxa (Biro et al. 2003; Réale et al. 2007; Biro and Stamps 2008).