Sex allocation and sex-ratio conflict in viscous populations

Abstract

In a social context, natural selection favours traits that maximize their bearers’ inclusive fitness, obtained through their own and their social partners’ reproduction. Such traits can be detrimental to its bearer, but can still be favoured if they are beneficial for others in a situation of higher relatedness among interacting social partners. Population viscosity—whereby a low rate of dispersal leads to a local concentration of relatives—has been suggested as one mechanism for generating higher relatedness to promote social evolution. However, local competition among relatives for resources can negate—or even completely cancel out—the effect of relatedness, limiting the impact of population viscosity on social evolution. Sex allocation—the apportionment of reproductive resources to male versus female function—is a social trait that may be modulated by relatedness and hence potentially by population viscosity. Moreover, in sexually asymmetric systems of genetic inheritance, there may also be an evolutionary conflict of interest between mother and father over the sex ratio of their offspring. In this thesis, I investigate how demographic and genetic factors impact upon the evolution of sex allocation and sex ratio conflict in viscous populations. To do so, I develop mathematical models to investigate how variation in rate and pattern of dispersal, genetic inheritance system and mating system impact upon the trade-off between production of males and females from perspective of parents. I perform computer simulations and experimental evolution using spider mites to test my analytical predictions.

Date of Award	30 Jun 2026
Original language	English
Awarding Institution	University of St Andrews
Supervisor	Andy Gardner (Supervisor)