Digest: Sex-specific benefits of mitochondrial introgression

Disrupting mitochondrial and nuclear co-adaptation is expected to reduce fitness, especially in males and with age. But is that always true? Garlovsky et al. (2025) tested this in a panel of Drosophila lines, assessing reproductive success across sex and age. Unexpectedly, new mitonuclear combinations had limited impact on reproduction and even conferred a fitness advantage to some males. These findings challenge current views, suggesting that mitochondrial replacement can sometimes enhance fitness.