Meiotic drive does not impede success in sperm competition in the stalk-eyed fly, Teleopsis dalmanni

Male X-linked meiotic drive systems, which cause the degeneration of Y-bearing sperm, are common in the Diptera. Sperm killing is typically associated with fitness costs that arise from the destruction of wildtype sperm and collateral damage to maturing drive sperm, resulting in poor success under sperm competition. We investigate X-linked meiotic drive fertility in the stalk-eyed fly, Teleopsis dalmanni. Drive male paternity was measured in double mating trials under sperm competition against a wildtype male. Drive males sired the same number of offspring as wildtype males, both when mated first or second. This is the first evidence that drive males can compete equally with non-drive males in double matings, challenging the assumption that drive males inevitably suffer reduced fertility. The finding is in accord with previous work showing that the number of sperm per ejaculate transferred to females during non-competitive single matings does not differ between drive and wildtype males, which is likely due to the adaptive evolution of enlarged testes in drive males. Future experiments will determine whether the competitive ability of drive males is maintained under higher rates of female remating likely to be experienced in nature.

Automated summary

In double mating trials, X-linked meiotic drive males in Teleopsis dalmanni (stalk-eyed fly) have been found to have the same level of fertility as wildtype males in sperm competition against wildtype males. This challenges the assumption that drive males inevitably have reduced fertility. Previous research has also shown that the number of sperm transferred to females during non-competitive single matings does not differ between drive and wildtype males, likely due to the adaptive evolution of enlarged testes in drive males. Future experiments will determine if the competitive ability of drive males is maintained under higher rates of female remating.