Evolution. 2025 Jul 30:qpaf153. doi: 10.1093/evolut/qpaf153. Online ahead of print.
ABSTRACT
Selfish genetic elements (SGEs) enjoy an evolutionary advantage by enhancing their own transmission to offspring, and their genetic suppressors are favoured when they re-establish fair inheritance patterns. Here, we study an X-linked Sex Ratio drive system (SR) in Drosophila subobscura, which kills Y-bearing sperm of SR males, resulting in the over-transmission of the SR-chromosome and a strong female-bias in their offspring. We surveyed D. subobscura populations in North Africa, which naturally harbour SR, and find that suppression occurs in ∼13.5% of wild-derived lines. We characterise this suppression phenotype though a series of crossing experiments, including multigenerational introgression of SR chromosomes into a suppressing genetic background. We show that introgression can restore normal offspring sex ratios, or, in some cases, result in an excess of male offspring. This suppression appears to be a multilocus trait, involving autosomes and the Y-chromosomes. Suppression of SR fails to ameliorate all costs of drive, with fully suppressed SR-carrying males having depressed fertility and low offspring egg hatch rates. Further, examination of internal male reproductive organs using microscopy suggests that suppressed SR males also have abnormal testes. These factors may explain why the suppression fails to reach high frequencies, despite the strong advantage of suppressing SR.
PMID:40736509 | DOI:10.1093/evolut/qpaf153
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