Abstract
Mate choice is an important driver of the evolution of sexual traits and can promote divergence and speciation. Understanding the underlying variation in mate choice decisions is crucial to understand variation in the strength and direction of sexual selection. We explored whether variation in the social environment influences mate choice decisions and focus on the aspect of mate choice termed choosiness (i.e. the effort invested in mate assessment and acquisition). Using call playbacks, we manipulated the social environment female green tree frogs would experience as they entered a chorus, and then we conducted two-choice playback trials to assess whether females exhibited social plasticity in choosiness. We explored social plasticity at 2 levels: in one experiment, we manipulated the presence or absence of preferred (attractive) and less preferred (unattractive) conspecific males (i.e. intraspecific context), and in the other experiment, we manipulated the presence or absence of preferred (conspecific) and less preferred closely related heterospecific males (i.e. interspecific context). We found that in the intraspecific context, the presence of attractive males increased choosiness, while absence of attractive males reduced choosiness. In the interspecific context, choosiness remained stable in most treatments, but was lowered when females experienced a mixture of conspecific and heterospecific calls. We discuss the effect of social plasticity in choosiness on mate choice decisions and highlight its evolutionary consequences.