Academic journal article Genetics

Multilevel Selection 1: Quantitative Genetics of Inheritance and Response to Selection

Academic journal article Genetics

Multilevel Selection 1: Quantitative Genetics of Inheritance and Response to Selection

Article excerpt

ABSTRACT

Interaction among individuals is universal, both in animals and in plants, and substantially affects evolution of natural populations and responses to artificial selection in agriculture. Although quantitative genetics has successfully been applied to many traits, it does not provide a general theory accounting for interaction among individuals and selection acting on multiple levels. Consequently, current quantitative genetic theory fails to explain why some traits do not respond to selection among individuals, but respond greatly to selection among groups. Understanding the full impacts of heritable interactions on the outcomes of selection requires a quantitative genetic framework including all levels of selection and relatedness. Here we present such a framework and provide expressions for the response to selection. Results show that interaction among individuals may create substantial heritable variation, which is hidden to classical analyses. Selection acting on higher levels of organization captures this hidden variation and therefore always yields positive response, whereas individual selection may yield response in the opposite direction. Our work provides testable predictions of response to multilevel selection and reduces to classical theory in the absence of interaction. Statistical methodology provided elsewhere enables empirical application of our work to both natural and domestic populations.

(ProQuest Information and Learning: ... denotes formulae omitted.)

IT is universally recognized that all plants and animals compete within or across species. These competitive interactions have important implications both for domestic breeding and for the outcome of evolutionary processes (GOODNIGHT and STEVENS 1997; KELLER 1999; CLUTTON-BROCK 2002). With respect to domestication and agriculture, reduction of competition and fighting and sharing of resources is critical for improving animal well-being and productivity in confined high-intensity rearing conditions (MUIR 2005). Competition and fighting behavior is also a major limitation as to which species can be domesticated (DIAMOND 2002). Understanding how to reduce competitive interactions in artificial breeding programs could improve animal well-being of those species that are currently being used in animal agriculture, such as swine and poultry (DENISON et al. 2003; MUIR 2003), and also expand the range of species that can be domesticated, such as carnivorous and/or cannibalistic shell- and game fish. Even with domesticated species, classic quantitative genetic theory fails to explain why some traits, in particular those related to behavior, fail to respond to selection, even though there is heritable variation and a positiveselectiondifferential (e.g.,TEICHERTCODDINGTON and SMITHERMAN 1988; VANGEN 1993; KRUUK et al. 2001). Generalization of quantitative genetic theory is required to understand how interactions among individuals (WOLF et al. 1998) and selection acting on multiple levels of organization affect response to selection (GRIFFING 1967; GOODNIGHT 2005).

With respect to evolutionary outcomes, there are several important issues that require a general concept of how competition influences adaptations within and between species. One of those issues is the evolution of altruism (WILSON 1985, 2005; WOODCOCK and HEATH 2002; FEHR and FISCHBACHER 2003; COOPER and WALLACE 2004; HAMILTON and TABORSKY 2005; OKASHA 2005) and the importance of kin selection to this process (HAMILTON 1964; MICHOD 1982; DAY and TAYLOR 1997; GRIFFIN and WEST 2002; AXELROD et al. 2004; GOODNIGHT 2005; WILSON 2005). At the heart of the debate is how cooperation and altruism can persist in the face of cheating (WADE and BREDEN 1980; HAMILTON and TABORSKY 2005). Some have suggested that the solution to this problem is the level of selection (SLATKIN and WADE 1978; WADE 1978; WILSON and SOBER 1994; KELLER 1999; GOODNIGHT 2005; WILSON 2005). In both biology and the human sciences, social groups are sometimes treated as adaptive units, whose organization cannot be reduced to the individual level. …

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