 The origins of ecological genetics are founded in the “modern synthesis” (Huxley 1942), where the integration of genetics and Darwinian evolution was achieved through the theoretical works of R. A. Fisher, S. Wright, and J. B. S. Haldane and the conceptual works and influential writings of J. Huxley, T. Dobzhansky, and H. J. Muller. From these genetic beginnings, it was natural for much evolutionary research to be concentrated on the forces that cause changes in gene and genotype frequencies within populations. In this genetics-centered view, the four evolutionary forces (mutation, random genetic drift, natural selection, and gene flow) act within and among populations to cause micro-evolutionary change. Those same forces act in concert to convert the genetic variation within populations into more or less permanent genetic variation between species. Given enough time, the micro-evolutionary forces are believed to be sufficient to account for macro-evolutionary patterns characteristic of the higher taxonomic groups. In short, the central challenge of the field of evolutionary genetics has been to describe how the four evolutionary forces shape patterns of gene, genome and species diversity, with a particular emphasis on the predominant role of natural selection among the several evolutionary forces.