Intralocus sexual conflict is a type of sexual conflict that occurs when a genetic locus harbours alleles which have opposing effects on the fitness of each sex, such that one allele improves the fitness of males (at the expense of females), while the alternative allele improves the fitness of females (at the expense of males).[1] Such "sexually antagonistic" polymorphisms are ultimately generated by two forces: (i) the divergent reproductive roles of each sex, such as conflicts over optimal mating strategy,[2][3] and (ii) the shared genome of both sexes, which generates positive between-sex genetic correlations for most traits.[4] In the long term, intralocus sexual conflict is resolved when genetic mechanisms evolve that decouple the between-sex genetic correlations between traits. This can be achieved, for example, via the evolution of sex-biased or sex-limited genes.
Intralocus sexual conflict can be considered a form of maladaptation,[5] as it results in a deviation of both sexes from their fitness optima, with both sexes expressing traits that are sub-optimal for that sex's fitness. Intralocus sexual conflict can also be considered a form of pleiotropy, in which genetic variants have opposing effects on different classes of individual within a population (i.e., males and females), rather than opposing effects on different components of fitness (e.g. survival vs. mating success). Intralocus sexual conflict has important implications for the evolution of sexual dimorphism,[6] the evolution of sex chromosomes[7][8] and the maintenance of genetic variation.[9]