Here we investigate intraspecific variation in diel patterns of acoustic signalling in the bladder grasshopper, Bullacris unicolor. We observed that B. unicolor calls at different times during the night in different parts of its distribution. Males further north typically call just before dawn, while those further south signal throughout the night. Sound transmission experiments were conducted in order to determine whether the observed discrepancy in signal timing can be explained by differences in signal propagation at different times in the night, which might vary geographically. We found significant differences in signal attenuation and fidelity at different broadcast times as well as between locations. However, there was only partial support for the hypothesis that males time their calls to coincide with the most ideal transmission conditions. We suggest that other factors, such as predation pressure, might also contribute to the observed discrepancy in signal timing between populations.
Mechanisms of reproductive isolation among sympatric broadcast-spawning corals of the Montastraea annularis species complex. —
Evolution of temporal isolation in the wild: genetic divergence in timing of migration and breeding by introduced chinook salmon populations. —