Digest: survival of the fittest in an admixed seabass population

Relatively few studies have assessed the impacts of introgression on traits associated with fitness. Leitwein et al. (2025) address this key question using an admixed population of European seabass found in the Western Mediterranean that results from hybridization between Atlantic and Mediterranean populations. They find that fish with a higher ratio of Atlantic ancestry exhibit phenotypes associated with reduced fitness, demonstrating that introgression in this case is disadvantageous.