Quantitative Traits and Phenotypic Interference

The theory of the evolution of quantitative traits is a topic, which has generated a lot of interest in recent years due to experimental data becoming much more easily available. With experimental methods increasingly able to measure systemsbiological amounts of data, theory needs to go beyond the so far established independent evolution of quantitative traits. This thesis investigates the asexual evolution of quantitative traits in two scopes. In the small scope we look at a single quantitative trait being influenced by external adaptation in genetically linked parts of the genome. In the grand, systems-biology scope we look at the whole organism with multiple linked quantitative traits. The statistics of a quantitative trait are negatively influenced by external linkage effects, where the effect can be described by a single parameter, the neutrality threshold. For the systemsbiological scope we study the effect of joint linkage on traits with biophysical fitness landscapes. The surprising result, due to this phenotypic interference, is a faster-than-linear increase of the genetic load with the number of co-evolving phenotypes. As a consequence, this provides us with a biophysically grounded explanation for the evolution of sex. The negative effects of linkage on adaptation and adaptability link these topics together with a chapter on Mendelian traits in asexual genomes. There we focus on the decreased ability to retain information in large, fast adapting genomes. Additionally, we find a new class of punctuated fitness waves, where periods of maintainance of function are interrupted by bursts of adaptation