Complex choice environments shelter unattractive signallers from sexual selection

For many animals, options abound when choosing a mate in socially complex
environments like a breeding chorus or lek. In such environments,
receivers often choose their mate based on individual differences in
signal repetition rate. However, signallers also differ in the regularity
with which they produce repeated signals. Irregularity in signalling
introduces uncertainty in decision-making by masking the among-individual
variation in signalling rate that is a target of mate choice. At present,
we know little about how the complexity of the choice environment impacts
selection on rate and regularity, two signalling behaviours that receivers
can only compare after sampling series of signals produced by multiple
signallers. In this study of female grey treefrogs (Hyla chrysoscelis), we
measured multivariate sexual selection on the rate and regularity of male
calling behaviour using two-, four-, and eight-choice tests. Receivers
overwhelmingly chose faster, more regular calling rates in two-choice
tests, but did so markedly less often when they chose among four or eight
stimuli. Signalling behaviour became much less predictive of signallers’
relative fitness as choice complexity increased, suggesting noise and
choice overload effects may shelter male phenotypes from sexual selection
imposed by female choice in complex social environments.