Broad Selectivity for Courtship Song in the Cricket Gryllus
bimaculatus
L.S. Shestakov & V.Yu. Vedenina
Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, Russia
E-mail: vedenin@iitp.ru
Аннотация
Various characteristics of a long-distance acoustic signal have been shown
to vary to different degrees. It has been suggested that female preferences
based on stable song parameters are stabilising or weakly directional, and
preferences based on variable parameters are strongly directional. We
tested this hypothesis based on a short-distance signal (courtship song)
produced by the field cricket, Gryllus bimaculatus. We studied the degree of
variability of different courtship song parameters and the behavioural
importance of several parameters using synthesised song models in playback
experiments. We found that most of the courtship song elements of
G. bimaculatus were quite variable (coefficient of variation, CV, in the
range of 20–53%). The most variable parameter of the courtship song was
the relative amplitude of two elements: high-amplitude ticks and lowamplitude
pulses. Because songs containing only ticks (of rare occurrence)
appeared to be more effective than songs with both ticks and pulses (of
frequent occurrence), we consider female preferences to be directional.
Alteration of less variable traits, such as the carrier frequency and duration
of ticks (CV = 20–25%), had a different effect on female responsiveness.
The synthesised songs with different carrier frequencies of ticks were
as attractive to females as the positive control (courtship of muted males
accompanied by playback of the recorded song). Altering the duration of
ticks had a crucial effect on the female response rate, decreasing female
responsiveness to the level observed in the negative control (courtship of
muted males). Thus, we did not find a strong relationship between the
variability of individual song parameters and their potential importance in
song recognition and the evaluation of male quality. The partial inconsistency
of our results with the data of other authors may be due to different
patterns of past and current selection on long-distance and short-distance
acoustic signals.