Sex-differential selection favors the evolution of biased RXI.

<p>Black curves are based on <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003440#pgen.1003440.e017" target="_blank">eq. (8)</a> for the mutation-selection balance model of genetic variation; diamonds are based on numerical evaluation of the more exact <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003440#pgen.1003440.e011" target="_blank">eq. (7)</a>. Gray curves are based on <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003440#pgen.1003440.e018" target="_blank">eq. (9)</a> for sexually antagonistic alleles maintained by balancing selection. Results for the mutation-selection balance case assume equal male and female selection coefficients (<i>s_m</i> = <i>s_f</i>). Biases are further accentuated when <i>s_m</i>><i>s_f</i>; biases may be dampened or reversed when <i>s_m</i><<i>s_f</i>.</p

Transit time simulation

This r script simulates the number of generations until a successfully invading allele reaches polymorphic equilibrium under balancing selection. Output applies to figure 1 of the manuscript

R code for simulations

The R code file is commented and can be used to simulate data, illustrated in figures in the publication: Zajitschek, F. and T. Connallon. Antagonistic pleiotropy in species with separate sexes, and the maintenance of genetic variation in life-history traits and fitness. 2018. Evolution

Hitchhiking of a neutral allele

This r script simulates the hitchhiking effect caused by a successfully invading allele that evolves toward a polymorphic equilibrium. Output applies to figure 2 of the manuscript

Sex-Differential Selection and the Evolution of X Inactivation Strategies

<div><p>X inactivation—the transcriptional silencing of one X chromosome copy per female somatic cell—is universal among therian mammals, yet the choice of which X to silence exhibits considerable variation among species. X inactivation strategies can range from strict paternally inherited X inactivation (PXI), which renders females haploid for all maternally inherited alleles, to unbiased random X inactivation (RXI), which equalizes expression of maternally and paternally inherited alleles in each female tissue. However, the underlying evolutionary processes that might account for this observed diversity of X inactivation strategies remain unclear. We present a theoretical population genetic analysis of X inactivation evolution and specifically consider how conditions of dominance, linkage, recombination, and sex-differential selection each influence evolutionary trajectories of X inactivation. The results indicate that a single, critical interaction between allelic dominance and sex-differential selection can select for a broad and continuous range of X inactivation strategies, including unequal rates of inactivation between maternally and paternally inherited X chromosomes. RXI is favored over complete PXI as long as alleles deleterious to female fitness are sufficiently recessive, and the criteria for RXI evolution is considerably more restrictive when fitness variation is sexually antagonistic (<i>i.e.</i>, alleles deleterious to females are beneficial to males) relative to variation that is deleterious to both sexes. Evolutionary transitions from PXI to RXI also generally increase mean relative female fitness at the expense of decreased male fitness. These results provide a theoretical framework for predicting and interpreting the evolution of chromosome-wide expression of X-linked genes and lead to several useful predictions that could motivate future studies of allele-specific gene expression variation.</p></div

DFE sim n = 10 dimensions

DFE sim n = 10 dimension

DFE sim n = 25 dimensions

DFE sim n = 25 dimension

single locus simulations

single locus simulation

Species’ range dynamics depend on the balance between environmental change and genetic drift.

<p>Specifically, range limit evolution depends on two compound parameters: (1) the ‘cost of migration’, which is proportional to the mean dispersal distance of individuals of the species, as well as the steepness of the environmental gradient (i.e., the rate at which a trait optimum changes across space), and (2) ‘neighbourhood size’, which is inversely proportional to the local intensity of genetic drift. As Polechová [<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2006735#pbio.2006735.ref008" target="_blank">8</a>] demonstrates, species’ range dynamics, including the location and stability of range limits, are predicted by the relative magnitude of neighbourhood size versus the steepness of the environmental gradient. For example, with a shallow environmental gradient relative to neighbourhood size, the species’ range expands to fill all of the available habitat (blue plots). With a steep environmental gradient relative to neighbourhood size, the species’ range contracts, leading to extinction or a restricted or fragmented range (red plots). With a steepening environmental gradient (black plots), the neighbourhood size can be sufficiently large to maintain local adaptation and high population density through most of the range (see the regions between the vertical arrows). However, as the environmental gradient steepens, the threshold neighbourhood size required to maintain local adaptation increases. Eventually, the neighbourhood size falls below the threshold for local adaptation (black arrows note the threshold), and abrupt range limits arise.</p

Criteria for the evolution of RXI.

<p>Black curves are based on <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003440#pgen.1003440.e005" target="_blank">eq. (3)</a> for the mutation-selection balance model of genetic variation (in which case, the <i>x</i>-axis refers to the female selection coefficient, <i>s_f</i>). The gray curve is based on <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003440#pgen.1003440.e006" target="_blank">eq. (4)</a> for sexually antagonistic alleles maintained by balancing selection (here, the <i>x</i>-axis refers to the male selection coefficient: <i>t_m</i>). The area above each curve represents parameter space where unbiased RXI is not favored over PXI. RXI is favored under the complementary parameter space below each curve.</p