Guppies: Brain size affects responsiveness in mating behavior to variation in predation pressure and sex‐ratio

Brain size affects responsiveness in mating behavior to variation in predation pressure and sex‐ratio. Alberto Corral‐López  Maksym Romensky  Alexander Kotrschal  Severine D. Buechel  Niclas Kolm. Journal of Evolutionary Biology, October 14 2019. https://doi.org/10.1111/jeb.13556

Abstract: Despite ongoing advances in sexual selection theory, the evolution of mating decisions remains enigmatic. Cognitive processes often require simultaneous processing of multiple sources of information from environmental and social cues. However, little experimental data exist on how cognitive ability affects such fitness‐associated aspects of behavior. Using advanced tracking techniques, we studied mating behaviors of guppies artificially selected for divergence in relative brain size, with known differences in cognitive ability, when predation threat and sex‐ratio was varied. In females, we found a general increase in copulation behavior in when the sex‐ratio was female biased, but only large‐brained females responded with greater willingness to copulate under a low predation threat. In males, we found that small‐brained individuals courted more intensively and displayed more aggressive behaviors than large‐brained individuals. However, there were no differences in female response to males with different brain size. These results provide further evidence of a role for female brain size in optimal decision‐making in a mating context. In addition, our results indicate that brain size may affect mating display skill in male guppies. We suggest that it is important to consider the association between brain size, cognitive ability and sexual behavior when studying how morphological and behavioral traits evolve in wild populations.