Digest: A sex chromosome driver without a sperm deficit.

Meiotic drivers that act during spermatogenesis derive a transmission advantage by disabling sperm that do not carry the driver, often leading to substantially reduced overall sperm number and function. A new study by Bates et al. (2023) shows no sperm deficit for a driver in a stalk-eyed fly, in contrast to a related species. This observed sperm compensation is possibly due to secondary testes-expanding mutations linked to the driving genomic locus.