Experiments confirm a dispersive phenotype associated with a natural gene drive system

Abstract

Meiotic drivers are genetic entities that increase their own probability of being transmitted to offspring, usually to the detriment of the rest of the organism, thus ‘selfishly’ increasing their fitness. In many meiotic drive systems, driver-carrying males are less successful in sperm competition, which occurs when females mate with multiple males in one oestrus cycle (polyandry). How do drivers respond to this selection? An observational study found that house mice carrying the t haplotype, a meiotic driver, are more likely to disperse from dense populations. This could help the t avoid detrimental sperm competition, because density is associated with the frequency of polyandry. However, no controlled experiments have been conducted to test these findings. Here, we confirm that carriers of the t haplotype are more dispersive, but we do not find this to depend on the local density. t -carriers with above-average body weight were particularly more likely to disperse than wild-type mice. t -carrying mice were also more explorative but not more active than wild-type mice. These results add experimental support to the previous observational finding that the t haplotype affects the dispersal phenotype in house mice, which supports the hypothesis that dispersal reduces the fitness costs of the t .

Selfish migrants: How a meiotic driver is selected to increase dispersal

“…As described in the introduction, the consequences of t haplotype homozygosity can be either inviability or male sterility. While we focused primarily on inviable t / t (the case for the t variant in which dispersal effects were studied in Runge and Lindholm (2018) & Runge and Lindholm (2021)), we also examined conditions in which t / t were infertile as males, but fully viable (Lewontin (1962); ). In this case we assumed that they approach females and mate with them normally, but are completely ignored as potential sires.…”

“…As a whole, we expect the costs and benefits of dispersal to differ between the wildtype and the t haplotype. Indeed, our previous empirical work on free‐living wild house mice found that t ‐carrying juveniles were more likely to emigrate, and were over‐represented in migration events (Runge & Lindholm, 2018, see Figure 1) as well as among dispersers in experimental setups (Runge & Lindholm, 2021).…”

Selfish migrants: How a meiotic driver is selected to increase dispersal

“…As described in the introduction, the consequences of t haplotype homozygosity can be either inviability or male sterility. While we focused primarily on inviable t / t (the case for the t variant in which dispersal effects were studied in Runge and Lindholm (2018) & Runge and Lindholm (2021)), we also examined conditions in which t / t were infertile as males, but fully viable (Lewontin (1962); τ = 1.0). In this case we assumed that they approach females and mate with them normally, but are completely ignored as potential sires.…”

“…As a whole, we expect the costs and benefits of dispersal to differ between the wildtype and the t haplotype. Indeed, our previous empirical work on free-living wild house mice found that t -carrying juveniles were more likely to emigrate, and were over-represented in migration events (Runge and Lindholm (2018), see Figure 1) as well as among dispersers in experimental setups (Runge and Lindholm 2021).…”

The effect of mating complexity on gene drive dynamics

“…It should be noted that despite substantial speculation and experimentation with autosomal natural gene drives, particularly the t-haploytpe in mice, there is no reliable evidence that mate choice has evolved (Sutter and Lindholm, 2016). However, behavioural traits that do appear to be linked to a drive locus have been recently described (Runge and Lindholm, 2021). Regardless, it is still potentially valuable to examine the relative sensitivity of various types of gene drive to the impact of mate choice should it evolve.…”