Tie that binds - Hill-Robertson Interference can produce signals of sexual antagonism even in the absence of sexually antagonistic selection

Sexually antagonistic (SA) selection on a trait with a shared genetic basis between the sexes is thought to lead to Intralocus Sexual Conflict (IaSC). A common way of measuring IaSC involves characterising the joint distribution of breeding values of male and female fitness using the intersexual additive genetic correlation for fitness ( r _{mf , W} ). However, there is considerable variation in the empirical estimates of r _{mf , W} - with estimates ranging from significantly negative (suggestive of strong IaSC) to significantly positive (suggesting an absence of IaSC) - even among closely related populations of the same species. Here, we investigate whether SA selection is even necessary for r _{mf , W} to be negative. We first highlight that the sign of r _{mf , W} depends on a term that describes direct sex-specific selection, and another that describes indirect selection mediated by linkage disequilibria (LD). We show that r _{mf , W} can be negative if (1) selection is perfectly sex-limited - such that every locus affects the fitness of one sex only - and (2) the LD between closely-linked male-beneficial and female-beneficial alleles is on average negative as predicted under Hill-Robertson Interference (HRI). We test this idea using individual-based simulations. Our results suggest that populations evolving under purely sex-limited selection exhibit a prominent negative bias in r _{mf , W} that gets strengthened by a reduction in the recombination rate. Therefore, HRI can drive r _{mf , W} to be negative even in the absence of SA selection suggesting that negative estimates of r _{mf , W} should not automatically be considered as evidence of IaSC.