Digest: Cave isolation relaxes purifying selection across catfish genomes

How does long-term cave isolation shape the efficacy of natural selection across cavefish genomes? Policarpo et al. (2026) show that dispensable light-related genes accumulate loss-of-function mutations neutrally in cavefish populations, and find genome-wide signatures of reduced selection efficacy in an ancient cavefish species. This work raises questions about whether prolonged isolation in cave environments inevitably leads to lower purifying selection and genomic erosion.