Using replicate populations evolved under the same environmental conditions, experimental evolution provides the unique opportunity to study polygenic adaptation. I will discuss how genetic redundancy, pleiotropy, epistasis and linkage disequilibrium influence the selection response of polygenic traits.
For over a century, most biologists have been convinced that all aspects of biodiversity have been driven entirely by natural selection, with stochastic forces and mutation bias playing a minimal role. However, this is not the case at the molecular and cellular levels, where diverse traits scale with cell/organism size in ways that cannot be explained by optimization and/or speed vs. efficiency arguments. These include aspects of gene/genome architecture, intracellular error rates, the multimeric nature of proteins, swimming efficiencies, and maximum growth rates.
Although natural selection may be the most powerful force in the biological world, it is not all powerful, and the power of random genetic drift ultimately dictates what selection can and cannot accomplish. Many prokaryotes may reside in population-genetic environments where the limits to selection are indeed dictated only by the constraints of cell biology. However, in the eukaryotic domain, larger organism size is typica...
