PHENOTYPIC VARIATION IN THE MATING PREFERENCES OF FEMALE FIELD CRICKETS, GRYLLUS INTEGER

Phenotypic variation in the mating preferences of female field crickets was examined. Males of this species produce a trilled calling song which varies in the number of pulses per trill, the inter-trill interval and the proportion of missing pulses within a trill. As a population, females preferred male calling songs with more pulses per trill and shorter inter-trill intervals in two-speaker choice tests, but did not discriminate between male song that varied in the proportion of missing pulses. Female preference functions were examined by sequentially presenting females with a series of songs that varied in only one parameter. As a population, the strength of the female preference for male calling song appeared to increase with the number of pulses per trill in the song. However, there was no significant variation in the strength of the preference for male calling song with either the inter-trill interval or proportion of missing pulses in the song. There was significant variation between individual females in their preference functions based on the number of pulses per trill and the inter-trill interval in male song, but not based on the proportion of missing pulses in male song. Females appeared to differ in how strongly they preferred more pulses per trill. In contrast, females appeared to differ not only in the strength of their preference based on inter-trill interval, but also in whether they preferred longer or shorter inter-trill intervals. The repeatability of preference functions within females was relatively high for number of pulses per trill (0.50) and inter-trill interval (0.59), but low for proportion of missing pulses (-0.02). Correlations between female preference functions were also examined. Females that strongly preferred more pulses per trill tended to strongly prefer shorter inter-trill intervals. In addition, females that strongly preferred shorter inter-trill intervals tended to prefer a higher proportion of missing pulses. These results suggest that selection can act on female preference functions in field crickets, and that direct selection on one preference function can result in indirect selection on other preference functions.