PMID: 19154391;Abstract:
Discrete behavioral strategies comprise a suite of traits closely integrated in their expression with consistent natural selection for such coexpression leading to developmental and genetic integration of their components. However, behavioral traits are often also selected to respond rapidly to changing environments, which should both favor their context-dependent expression and inhibit evolution of genetic integration with other, less flexible traits. Here we use a multigeneration pedigree and long-term data on lifetime fitness to test whether behaviors comprising distinct dispersal strategies of western bluebirds - a species in which the propensity to disperse is functionally integrated with aggressive behavior - are genetically correlated. We further investigated whether selection favors flexibility in the expression of aggression in relation to current social context. We found a significant genetic correlation between aggression and dispersal that is concordant with consistent selection for coexpression of these behaviors. To a limited extent, individuals modified their aggression to match their mate; however, we found no fitness consequences on such adjustments. These results introduce a novel way of viewing behavioral strategies, where flexibility of behavior, while often aiding an organism's fit in its current environment, may be limited and thereby enable integration with less flexible traits. © 2009 The Author(s).
Abstract:
Behavior has been viewed as a pacemaker of evolutionary change because changes in behavior are thought to expose organisms to novel selection pressures and result in rapid evolution of morphological, life history and physiological traits. However, the idea that behavior primarily drives evolutionary change has been challenged by an alternative view of behavior as an inhibitor of evolution. According to this view, a high level of behavioral plasticity shields organisms from strong directional selection by allowing individuals to exploit new resources or move to a less stressful environment. Here, I suggest that absence of clear mechanisms underlying these hypotheses impedes empirical evaluation of behavior's role in evolution in two ways. First, both hypotheses focus on behavioral shifts as a key step in the evolutionary process but ignore the developmental mechanisms underlying these shifts and this has fostered unwarranted assumptions about the specific types of behavioral shifts that are important for evolutionary change. Second, neither hypothesis provides a means of connecting within-individual changes in behavior to population-level processes that lead to evolutionary diversification or stasis. To resolve these issues, I incorporate developmental and evolutionary mechanisms into a conceptual framework that generates predictions about the types of behavior and types of behavioral shifts that should affect both micro and macroevolutionary processes. © Springer Science+Business Media B.V. 2008.
