Sex-biased demography modulates male harm across the genome

Abstract

Recent years have seen an explosion of theoretical and empirical interest in the role that kin selection plays in shaping patterns of sexual conflict, with a particular focus on male harming traits. However, this work has focused solely on autosomal genes, and as such it remains unclear how demography modulates the evolution of male harm loci occurring in other portions of the genome, such as sex chromosomes and cytoplasmic elements. To investigate this, we extend existing models of sexual conflict for application to these different modes of inheritance. We first analyse the general case, revealing how sex-specific relatedness, reproductive value and the intensity of local competition combine to determine the potential for male harm. We then analyse a series of demographically explicit models, to assess how dispersal, overlapping generations, reproductive skew and the mechanism of population regulation affect sexual conflict across the genome, and drive conflict between nuclear and cytoplasmic genes. We then explore the effects of sex biases in these demographic parameters, showing how they may drive further conflicts between autosomes and sex chromosomes. Finally, we outline how different crossing schemes may be used to identify signatures of these intragenomic conflicts.

Keywords: cytoplasmic inheritance; intragenomic conflict; overlapping generations; sex chromosome; sexual conflict; soft selection.

Figure 1.

Demography modulates the potential for harm H differently across the genome. (a) Demographic factors modulate harm differently between nuclear (N: autosomes, X, Y, Z) and cytoplasmic genes (C), with differences dependent on the extent of paternal transmission λ. In panels (ii–iv), d = 0.5. (b) Sex differences in demographic parameters such as (i) dispersal (d_f = 0.5), (ii) survival rate (l_f = 0.5), (iii) reproductive skew (γ_f = 0.5) and (iv) population regulation (s_f = 0.5), uncouple the interests of nuclear genes with respect to male harm. In panels (ii–iv) d_f = d_m = 0.5. Across all panels n = 5. Full methods to recreate these plots can be found in the electronic supplementary material, §2. (Online version in colour.)