Environment-dependent use of mate choice cues in sticklebacks

Human-induced environmental changes alter terrestrial and aquatic ecosystems worldwide. This influences also evolutionary processes, such as sexual selection, by constraining mate choice and mate competition. Organisms often use multiple cues in mate choice, with different cues indicating the same or different benefits. Because the assessment and information content of cues can vary with environmental conditions, changes in the environment could alter mate choice. Here we determined if increased phytoplankton turbidity influences the relative use of olfactory and visual cues in mate choice in the three-spined stickleback Gasterosteus aculeatus. In a mate choice experiment, we found that females relied more on visual than olfactory cues in clear water. However, in turbid water, the pattern was the opposite with olfactory cues being more important than visual cues. Interestingly, mate preferences based on visual and olfactory cues did not agree, which suggests that human-induced environmental change could shift mate choice. This could influence the direction and target of sexual selection and have further consequences for the viability of the population under the new conditions.