Scientists have identified a unique spider species, Dysdera tilosensis, on the Canary Islands that has halved its DNA content while maintaining high genetic diversity. This unprecedented genome downsizing, detailed in Molecular Biology and Evolution, challenges conventional understanding of evolutionary processes. Researchers from the University of Barcelona, collaborating with CSIC and the University of Neuchâtel, compared this island species to its mainland counterpart, Dysdera catalonica, revealing significant genetic differences.