  The introduction and persistence of novel sexually antagonistic alleles can
depend upon factors that differ between males and females. Understanding the
conditions for invasion in a two-locus model can elucidate these processes. For
instance, selection can act differently upon the sexes, or sex-linkage can
facilitate the invasion of genetic variation with opposing fitness effects
between the sexes. Two factors that deserve further attention are recombination
rates and allele frequencies -- both of which can vary substantially between
the sexes. We find that sex-specific recombination rates in a two-locus diploid
model can affect the invasion outcome of sexually antagonistic alleles and that
the sex-averaged recombination rate is not necessarily sufficient to predict
invasion. We confirm that the range of permissible recombination rates is
smaller in the sex benefitting from invasion and larger in the sex harmed by
invasion. However, within the invasion space, male recombination rate can be
greater than, equal to, or less than female recombination rate in order for a
male-benefit, female-detriment allele to invade (and similarly for a
female-benefit, male-detriment allele). We further show that a novel, sexually
antagonistic allele that is also associated with a lowered recombination rate
can invade more easily when present in the double heterozygote genotype.
Finally, we find that sexual dimorphism in resident allele frequencies can
impact the invasion of new sexually antagonistic alleles at a second locus. Our
results suggest that accounting for sex-specific recombination rates and allele
frequencies can determine the difference between invasion and non-invasion of
novel sexually antagonistic alleles in a two-locus model.
