1. Trade-offs play a fundamental role in the evolution of many traits. 2. In wing-polymorphic field crickets, the long-winged morph can disperse from unfavourable environments, but has lower reproductive success than the short-winged morph, because of costs associated with flight capability.3. However, long-winged individuals may minimise costs in favourable environments by histolysing their flight muscles and becoming flightless.4. Few studies have examined how flight-muscle histolysis affects male signalling and mate attraction.5. We examined differences in singing activity and song characteristics among the flightless (short-winged and histolysed long-winged) and the flight-capable male morphs, and female preferences for male song, in the sand field cricket. 6. We found: (i) both flightless morphs sang more than the flight-capable morph, (ii) song characteristics varied among the three morphs, and (iii) females preferred songs characteristic of the long-winged morphs.7. Histolysis should increase mating success of long-winged males because it increases singing activity.8. Histolysed long-winged males may have higher mating success than short-winged males as they sing as frequently but produce more attractive songs. 9. Therefore, plasticity within the long-winged morph may reduce costs of maturing in environments from which dispersal is not advantageous; non-flying morphs may be pursuing different reproductive tactics.
In many Lepidoptera species usually only males puddle for sodium. Two explanations have been offered for this: (1) neuromuscular activity: males need increased sodium for flight because they are more active flyers than females; and (2) direct benefits: sodium is a type of direct benefit provided by males to females via ejaculate during mating. Surprisingly, there is little direct experimental evidence for either of these. In this study, we examined both explanations using the pipevine swallowtail butterfly, Battus philenor L. If sodium increases neuromuscular activity, males consuming sodium should be better fliers than males without sodium. If males collect sodium for nuptial gifts that benefit their mates, males consuming sodium may have greater mating success than males without sodium. In that case, females then need an honest cue/signal of the quality of male-provided direct benefits that they can assess before mating. If sodium affects male courtship flight by increasing neuromuscular activity, how a male courts could serve as such a premating cue/signal of male benefit quality. Therefore, sodium may benefit males in terms of obtaining mates by increasing their neuromuscular activity. In this study we found that males that consumed sodium courted more vigorously and had greater mating success than males that consumed water. In addition, the courtship displays of males consuming sodium were significantly different from those of males consuming water, providing a possible honest cue/signal of male benefit quality that females can assess. Interestingly, we did not find evidence that sodium consumption affects male flight outside of courtship. That only aspects of male flight related to mating were affected by sodium, while aspects of general flight were not, is consistent with the idea that sodium may benefit males in terms of obtaining mates via effects on neuromuscular activity.
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