Multimodal signal compensation: do field crickets flexibly shift sexual signaling modality after the evolutionary loss of acoustic communication?

Several hypotheses could explain the evolution of multimodal signals.
One possibility is that such signals allow for communication even when
one signalling modality is temporarily unavailable. However, little is
known about the consequences of the permanent evolutionary loss of a
signal modality. We used the field cricket Teleogryllus oceanicus
to test the hypothesis that the loss of one mode of signalling can be
accommodated by flexibly switching to another pre-existing modality.
Field crickets use cues that carry social information in the form of
both long-range acoustic signals and short-range cuticular hydrocarbons
(CHCs), but males in some T. oceanicus populations have
permanently lost the ability to sing because of a morphological mutation
erasing sound-producing structures on their wings. In assays testing
responsiveness to substrate-borne CHCs, T. oceanicus females
responded to the presence of male, but not female, CHCs, which is
consistent with known sexual dimorphism in field cricket chemical cues.
However, we found no evidence for signal compensation in male crickets
that have experienced an evolutionary loss of acoustic signals: females
did not differentially respond to the CHCs of constitutively silent
males compared to those of normal males. The ability of organisms to
shift adaptively from one signalling modality to another following the
evolutionary loss of a signal is likely to be constrained by both the
degree to which signal production and receiving is flexible and the
existence of suitably preadapted alternative modalities.