Evolutionary Quantitative Genetics

Evolutionary quantitative genetics is concerned with the evolution of quantitative traits that are affected by many genes (e.g., body size, metabolic rate, competitive ability). Although evolutionary quantitative genetics has emerged as the dominant paradigm for understanding evolution, the full scope of its achievements are not yet apparent to a wide audience. To reach and engage that wider audience, this book summarizes important empirical and theoretical results in evolutionary quantitative genetics. Here are a few significant signposts along the path of the book’s main argument: (1) Analysis of a large literature on selection measured in nature indicates that most traits are close to, if not on, an adaptive peak. (2) QTL and GWAS studies have shown that quantitative traits are affected by scores or if not hundreds of genes (polygeny). (3) Most traits interact with other traits, forming functional complexes that are shaped by stabilizing and correlational selection. (4) Such trait complexes can persist for hundreds of millions of years, suggesting long-lasting patterns of multivariate selection. (5) Perpetual, random movement of the adaptive peak is the common denominator of successful models of adaptive radiation. A single model of adaptive radiation can produce stasis or exuberant diversification depending on the setting for the rate of peak movement. (6) Simulation studies of evolving multivariate inheritance suggest that processes of mutation, inheritance, and selection may evolve towards mutual alignment with the predominant directions of peak movement. (7) Evolutionary models of trait-based interaction between species (e.g., predators and prey) suggest that periods of maladaptation may be common and that trait means will equilibrate downslope from adaptive peaks. Evolutionary quantitative genetics (EQG) provides a formal theoretical foundation for quantitatively linking natural selection and genetic variation to the rate and expanse of adaptive evolution. It has become the dominant conceptual framework for interpreting the evolution of quantitative traits in terms of elementary forces (mutation, inheritance, selection, and drift). Despite this success, the relevance of EQG to many biological scenarios remains relatively unappreciated, with numerous fields yet to fully embrace its approach. Part of the reason for this lag is that conceptual advances in EQG have not yet been fully synthesized and made accessible to a wider academic audience. A comprehensive, accessible overview is therefore now timely, and Evolutionary Quantitative Genetics provides this much-needed synthesis. The central argument of the book is that an adaptive landscape concept can be used to understand both evolutionary process within lineages and the pattern of adaptive radiations. In particular, it provides a convincing argument that models with a moving adaptive peak carry us further than any other conceptual approach yet devised. Although additive theory holds center stage, the book mentions and references departures from additivity including non-Gaussian distributions of allelic effects, dominance, epistasis, maternal effects and phenotypic plasticity. This accessible, advanced textbook is aimed principally at students (from senior undergraduate to postgraduate) as well as practising scientists in the fields of evolutionary biology, ecology, physiology, functional morphology, developmental biology, comparative biology, paleontology, and beyond who are interested in how adaptive radiations are produced by evolutionary and ecological processes.