Effects of Ambient Temperature on the Recognition and Preferences for Host Song Pulse-rate by the Acoustic Parasitoid FlyOrmia ochracea

Abstract

Receivers of acoustic communication signals evaluate signal features to correctly identify conspecifics. Environmental variation such as changes in the ambient temperature can alter signal features that may render species recognition a challenge. In field crickets, song temporal features evaluated for species recognition vary with temperature, and the intended receivers of these signals exhibit signal preferences that are temperature-coupled to maintain effective communication. Whether eavesdroppers of communication signals exhibit similar temperature-coupled preferences is unknown. Here, we investigate whether the parasitoid flyOrmia ochracea, an eavesdropper of cricket calling songs, exhibit song pulse rate preferences that are temperature-coupled. We use a high-speed treadmill system to record walking phonotaxis at three ambient temperatures (21, 25, and 30 ℃) in response to songs that varied in pulse rates (20 to 90 pulses per second). Total walking distance, peak steering velocity, angular heading, and the phonotaxis performance index varied with song pulse rates and were affected by ambient temperature. The peak of phonotaxis performance index preference functions became broader and exhibited a high-pass shape, shifting to higher pulse rate values at higher temperatures. Temperature related changes in cricket songs between 21-30 ℃ will not drastically affect the ability of flies to recognize cricket calling songs.