Within-population variation in treefrog preference functions

The mate choice behaviors of females can greatly affect patterns of
reproductive success in males and influence the evolution of sexually
selected male traits. Population-level estimates of display preferences
may provide an accurate estimate of the strength and direction of
selection by female choice if all females in the population show
homogeneous preferences. However, population-level estimates may yield
misleading estimates if there is within-population variation in mate
preferences. While it is increasingly clear that the latter situation is
common in nature, empirical data on the magnitude of variation in female
preferences is required to improve our current understanding of its
potential evolutionary consequences. We explored variation in female
preference functions for three male call properties in a treefrog. We
found that at best 62% of females share a preference function shape with
the respective population curve. Population curves may accurately capture
the direction of sexual selection, but depending on the properties of the
constituting individual function they may over- or underestimate the
strength of selection. Particularly population estimates suggesting weak
selection may in fact hide the presence of individual females with strong
but opposing preferences.