The ecology of sex-ratio distorting meiotic driver

Gene drive systems are selfish genes that manipulate reproduction to enhance their transmission, at a cost to the rest of the genome. Currently, synthetic gene drive systems are being constructed for insertion into pest populations to eliminate or modify them. To be able to predict the outcome of such a release, we need to understand the dynamics of naturally occurring gene drive systems.
X chromosome meiotic drive (XCMD) is a key model for gene drive. In males, these selfish X chromosomes kill Y chromosome bearing sperm during spermatogenesis, so all functional sperm carry the driving X, and all offspring are daughters. This can allow XCMD to spread very rapidly through populations, distorting sex ratios, and potentially eliminating entire populations due to a lack of males. However, almost all XCMDs seen in nature are found at stable frequencies and do not spread. The reasons for this stability are not understood.
This project aims to investigate the factors preventing the spread of the XCMD "SRs" in the fruit fly Drosophila subobscura. SRs has been found at frequencies of 10-20% in North Africa for the past 50 years. It also cannot spread into European populations, due to incompatibilities between SRs and European autosomes.