Assessing the contribution of Dark DNA to rapid adaptive evolution – CODDE

Genetic variation is the primary source of variability on which evolution acts. However, the observation that species can evolve rapidly to cope with changing environments in the apparent absence of genetic variation poses a challenge for integration into standard evolutionary theory. In response to rapid environmental changes, organisms will first react by quickly modifying their phenotypes through phenotypic plasticity and, over longer periods, through evolutionary changes. Phenotypic plasticity is defined as the ability of a given genotype to produce different phenotypes depending on the environment, while evolution results in modifications to the genome. Most empirical and theoretical knowledge on this topic focuses on changes in the coding regions of the genome, without ever considering its repetitive components, particularly transposable elements (TEs), often referred to as 'junk DNA.' Most transposable elements have no functional role, but many are capable of contributing to the regulation of gene expression, as they harbor a wide range of regulatory sequences that can either increase or decrease gene expression levels. TEs are sensitive to environmental changes, suggesting a potential role in phenotypic plasticity and, therefore, in adaptive evolution in changing environments. However, so far, no clear quantification of TEs as an additional source of variation has been incorporated into models of evolution and population genetics. Here, we propose to test the links between TEs, plasticity, and adaptive evolution.