Signal assessment in Photinus greeni fireflies

Abstract

In Photinus fireflies, flying males emit bioluminescent courtship signals to which conspecific females selectively respond. Previous work has examined variation in male signals and female preference in firefly species with either single-pulse or multiple-pulse male signals. Little, however, is known about Photinus species such as Photinus greeni in which males emit paired pulses. We first examined variation in male P. greeni signals. Using playback experiments, in lab and in the field, we then independently manipulated male pulse duration and inter-pulse interval (IPI) to examine female P. greeni signal assessment. Early in the season when the sex ratio was male biased, we examined morphological and behavioral correlates of male mating success in competitive courtships. We hypothesized that if females assess male IPI for species recognition then (a) females should prefer mean male IPIs and (b) female responsiveness to male signals with different IPIs should be independent of female body condition. We found that females were most responsive to signals with mean male IPIs and that body condition did not affect female responsiveness to signals with differing IPI but did affect female responsiveness to signals with differing pulse duration. Across the range of male pulse durations and IPIs seen in the field, females responded less to male signals with different IPI. In competitive courtships, males that flashed at a high rate and elicited more female responses were more likely to mate. These data support our hypothesis that female P. greeni assess male IPI primarily for species recognition and suggest that male pulse duration and flash rate may be indicators of male quality