RT Journal Article
SR Electronic
T1 Flies improve the salience of iridescent sexual signals by orienting toward the sun
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2020.05.09.085639
DO 10.1101/2020.05.09.085639
A1 Thomas E. White
A1 Tanya Latty
YR 2020
UL http://biorxiv.org/content/early/2020/05/10/2020.05.09.085639.abstract
AB Sunlight is the ultimate source of most visual signals. Theory predicts strong selection for its effective use during communication, with functional links between signal designs and display behaviours a likely result. This is particularly true for iridescent structural colours, whose moment-to-moment appearance bears a heightened sensitivity to the position of signallers, receivers, and the sun. Here we experimentally tested this prediction using Lispe cana, a muscid fly in which males present their structurally coloured faces and wings to females during ground-based sexual displays. In field-based assays we found that males actively bias the orientation of their displays toward the solar azimuth under conditions of full sunlight and do so across the entire day. This bias breaks down, however, when the sun is naturally concealed by heavy cloud or experimentally obscured. Our modelling of the appearance of male signals revealed clear benefits for the salience of male ornaments, with a roughly four-fold increase in subjective luminance achievable through accurate display orientation. These findings offer fine-scale, causal evidence for the active control of sexual displays to enhance the appearance of iridescent signals. More broadly, they speak to predicted coevolution between dynamic signal designs and presentation behaviours, and support arguments for a richer appreciation of the fluidity of visual communication.Competing Interest StatementThe authors have declared no competing interest.