Natural habitats are rapidly changing due to climate change and globalization. This can break down mating barriers between species and lead to increased hybridization rates. How detrimental or beneficial hybridization is for population fitness and adaptation is usually unknown and depends on genetic and environmental factors. Here, we use a combination of experimental evolution with the model system yeast Saccharomyces cerevisiae and population genomics of natural populations of the filamentous fungus Podospora anserina to study adaptation and hybridization. Previously established artificial populations of S. cerevisiae were used to study the dynamics of adaptation in stressful environments, one of which contained lithium acetate. We observed that in this particular environment adaptation is extremely fast and associated with ploidy changes. Hence, the goal of this project is to 1) explore the reproducibility of previous experiments, and 2) to characterize at a finer scale the dynamics of parallel evolution to lithium acetate. We will keep using the storage and computing resources to characterize the genomic dynamics of this experiment. In addition, we will use forward simulations to understand the patterns that we see. The original adaptation experiments are also being used to study the effect of hybridization at various levels of adaptation to different stressful environment. On the other hand, using new sequencing data of P. anserina populations and related species, we will study historical demography and hybridization, in particular focusing on a specific class of genes that potentially function as a fungal immune system. Overall, these analyses will contribute to our understanding of adaptation and hybridization both in experimental and natural populations.