Using positive-to-negative behavioural responses to evaluate treefrog mate choice

Sexual competition hinges on the ability to impress other conspecifics, to
drive them away or attract them. In such cases, the selective environment
may be hedonic or affective in nature, as it consists of the evaluations
of the individuals making the decisions. This may contribute to the power
of sexual selection because evaluations may range from positive to
negative rather than simply from positive to neutral. Selection due to
mate choice may therefore be stronger than currently appreciated. Further,
change in preferred mate types can occur simply by changes (“flips”) in
the evaluation of similar display features, adding to the dynamism of
sexual selection as well as its strength. We tested the hypothesis of
positive-to-negative behavioural responses in mate choice with a playback
experiment using two treefrog species with "mirror image"
structures in their advertisement and aggressive calls. Female treefrog
responses ranged from approach to evasion, and the presence of an aversive
stimulus tainted evaluation of an attractive stimulus. Further, females in
the two species showed flips in approach/evasion of stimuli with
comparable signal structure. These results suggest that hedonic evaluation
may have an important role in mate choice, and showcase how mechanistic
analysis can help understand evolutionary processes.