Life history and mating systems select for male biased parasitism mediated through natural selection and ecological feedbacks

TL;DR

This study explores how mating systems and sex-specific life history traits drive the evolution of male-biased parasitism, emphasizing ecological feedbacks and natural selection in a host-parasite model.

Contribution

It demonstrates that sexual differences in lifespan and competition can lead to male-biased parasitism, highlighting the role of ecological feedbacks in this evolutionary process.

Findings

Male-biased parasitism evolves with shorter male lifespan.

Greater male competition for resources promotes male-biased parasitism.

Mating system variations do not directly cause bias but may enhance existing biases.

Abstract

Males are often the "sicker" sex with male biased parasitism found in a taxonomically diverse range of species. There is considerable interest in the processes that could underlie the evolution of sex-biased parasitism. Mating system differences along with differences in lifespan may play a key role. We examine whether these factors are likely to lead to male-biased parasitism through natural selection taking into account the critical role that ecological feedbacks play in the evolution of defence. We use a host-parasite model with two-sexes and the techniques of adaptive dynamics to investigate how mating system and sexual differences in competitive ability and longevity can select for a bias in the rates of parasitism. Male-biased parasitism is selected for when males have a shorter average lifespan or when males are subject to greater competition for resources. Male-biased parasitism evolves as a consequence of sexual differences in life history that produce a greater proportion of susceptible females than males and therefore reduce the cost of avoiding parasitism in males. Different mating systems such as monogamy, polygamy or polyandry did not produce a bias in parasitism through these ecological feedbacks but may accentuate an existing bias.