Parent-offspring conflict over sex determination in non-Mendelian systems

Abstract

Across the tree of life, many organisms exhibit asymmetric inheritance systems in which males and females contribute differently to the long-term genetic future of the population. Although, in such groups, the sexes ultimately differ in their contributions, the zygotes that become males and females often start out genetically identical, with sex determined by maternal factors deposited into the embryo. However, there has been little work considering what the optimal sex ratio is from the perspective of the offspring in such scenarios, how this may differ from their parents, and how such conflicts may be modulated by other ecological factors. To investigate this, we develop analytical models to calculate the optimal sex allocation under a range of asymmetric genetic systems, and under the control of different parties. We then investigate the effects of various population structures and mating systems to consider their effects in shaping such conflicts. We find that asymmetric genetic systems may be prone to perpetual ongoing conflict between mothers and offspring over sex determination, even in panmictic populations. This may be one factor explaining the diverse and unusual sets of sex determining systems seen in these groups.