Abstract
While a number of studies have measured multivariate sexual selection acting on sexual signals in wild populations, few have confirmed these findings with experimental manipulation. Sagebrush crickets are ideally suited to such investigations because mating imposes an unambiguous phenotypic marker on males arising from nuptial feeding by females. We quantified sexual selection operating on male song by recording songs of virgin and mated males captured from three wild populations. To determine the extent to which selection on male song is influenced by female preference, we conducted a companion study in which we synthesized male songs and broadcast them to females in choice trials. Multivariate selection analysis revealed a saddle-shaped fitness surface, the highest peak of which corresponded to longer train and pulse durations, and longer intertrain intervals. Longer trains and pulses likely promote greater mate attraction, but selection for longer intertrain durations suggests that energetic constraints may necessitate “time outs”. Playback trials confirmed the selection for longer train and pulse durations, and revealed significant stabilizing selection on dominant frequency, suggesting that the female auditory system is tightly tuned to the species-specific call frequency. Collectively, our results revealed a complex pattern of multivariate nonlinear selection characterized primarily by strong stabilizing and disruptive selection on male song traits.
Highlights
Male acoustic signals play an important role in mate attraction in a number of taxa including birds (Catchpole and Slater 1995), mammals (McComb 1991), anurans (Gerhardt and Brooks 2009), and insects (Alexander 1962; Huber et al 1989; Robinson and Hall 2002), and are a frequent target of sexual selection (Andersson 1994)
Ecology and Evolution published by John Wiley & Sons Ltd
There was, quadratic selection operating on dominant frequency (DF) and significant positive correlational selection between pulse duration (PD) and interpulse duration (IPD), and between train duration (TD) and intertrain duration (ITD) (Table 2A)
Summary
Male acoustic signals play an important role in mate attraction in a number of taxa including birds (Catchpole and Slater 1995), mammals (McComb 1991), anurans (Gerhardt and Brooks 2009), and insects (Alexander 1962; Huber et al 1989; Robinson and Hall 2002), and are a frequent target of sexual selection (Andersson 1994). Females may impose directional (linear) sexual selection on males by choosing mates that exhibit the greatest calling effort (e.g., Brooks et al 2005; Bentsen et al 2006; Gerhardt and Brooks 2009). Males that produce song beyond these intermediate thresholds might be expected to have lower reproductive success because they are not recognized as conspecifics or escape detection by the female auditory system
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