A study of tactical and sexual dimorphism in cognition with insights for sexual conflict

AbstractThe sexes may have different optima in cognitive traits due to differences in life history strategies and the expense of investing in metabolically costly brain tissue. However, given genetic correlations, each sex could be constrained from reaching its cognitive optimum due to intralocus sexual conflict. We compared learning performance of two male alternative reproductive tactics and females from known genotypes (both sire and dam) in the livebearing fish Xiphophorus multilineatus. We predicted that females’ learning performance would align with the learning performance of their sire’s genotype due to genetic correlation of cognitive traits. Using a classical conditioning assessment (associating a flashing light with a food reward), we detected mating tactic dimorphism in learning performance, with the behaviourally plastic sneaker males outperforming the behaviourally fixed courter males. Unexpectedly, females sired by the faster-learning sneaker males performed significantly worse than sneaker males. We also detected an influence of brain size on female learning performance. Previous studies have found that females invest more in offspring sired by courter males, and we therefore hypothesize that maternal effects could potentially mitigate the influence of sexual conflict on a cognitive trait.