Inferring the genetic architecture of adaptive traits

Identification of the genetic basis of adaptive traits has been one of the main questions in evolutionary biology. Recent studies have shown that most adaptive traits are polygenic with many contributing loci. Predominantly, the genetic basis of adaptive traits has been explained by the selective sweep paradigm. This paradigm states that beneficial alleles independently spread in population until fixation. However, an alternative explanation has also been provided. Trait optimum paradigm argues that many contributing loci are needed for a population to reach the optimal fitness. Distinction of these two paradigms requires innovative approaches. Computer simulations have shown that populations of different sizes have distinct features under the sweep and trait optimum paradigms. In this project, I will take advantage of the effect of population size for distinguishing between the two paradigms. Highly replicated D. simulans populations will be exposed to an extreme hot environment (29C) at two different population sizes (450 and 9000) and the evolutionary response on the genomic, transcriptomic, phenotypic and fitness level will be monitored every 20 generations. Taking advantage of the different predictions for the sweep and trait optimum paradigm, the relative importance of both adaptive architectures will be determined.