The eco-evolutionary dynamics of X-linked inversions and meiotic drive

The first part of the PhD will focus on the demographic effects of X-linked meiotic drive, and in particular how populations might persist for longer than in the absence of drive.

Genetic elements known as "meiotic drivers" violate Mendel's law of equal segregation by interfering with the process of meiosis to ensure they are transmitted to more than 50% of carriers' progeny.

In classic systems of X-linked meiotic drive, X-bearing sperm are produced in excess by males, which leads to female-biased sex ratios. In a seminal work, Hamilton showed that these selfish sex chromosomes can drive populations to extinction because males become vanishingly rare. However, he also noted that, at the group level, the optimal sex ratio is likely to be somewhat female biased because only a small number of males are required for fertilisation.

I aim to develop eco-evolutionary models that track demographic dynamics as well as the spread of sex-linked meiotic drive alleles, and find conditions under which X-linked meiotic drive alleles spread and then reach in intermediate frequency or fixation, while considering different levels of sperm competition and polyandry.

We hypothesise that X-linked meiotic drive alleles that do not reach fixation will boost population sizes and persistence times, demonstrating that selfish genetic elements can move sex ratios closer to their population-level optimum. As a consequence it may be the case that researchers should consider the potential for ecologically beneficial side effects of sex-linked meiotic drive, especially in light of proposals to use meiotic drive for biological control.


Following from this, we will consider the dynamics of an X chromosome linked inversion. Meiotic drive systems are often found within inversions and this is often cited in the literature as a reason for fitness costs in females, as inversions may accrue deleterious mutations which cannot be purged due to their reduced rate of recombination. As such, the static cost to females often assumed may be unrealistic as a recent driving allele will not have had time to get these mutations. We will ask whether fitness costs would rise quickly enough to slow down the spread of the driving allele, preventing it from fixing and causing population extinction.