Communication among individual animals is essential for survival and reproduction. Across animals, communication signals are incredibly diverse and employ a variety of senses, ranging from vision to smell. This project seeks to determine how and why signals differ among species in the charismatic insect group, the fireflies. While the public is most familiar with their flashing signals on warm summer nights, used to find and locate mates, a number of firefly species have lost the ability to produce light as adults. Unlike their lighted counterparts, these “unlighted†adult fireflies are day-active, and studies suggest that they use smell to detect the chemical signals (pheromones) of potential mates. By comparing North American firefly species that use light versus pheromone signals, there is the potential to identify common patterns in the chemical, genetic, and behavioral changes associated with switching signal modes. The resources produced during this project will dramatically expand genomic tools for fireflies, enabling substantial advances in evolutionary, natural products, and conservation studies. The pheromones identified can open up new possibilities for surveillance of threatened unlighted firefly populations that are otherwise relatively difficult to census. Fireflies also offer an ideal opportunity for public outreach, as they are charismatic insects that draw public interest. Development of educational modules in insect biology and conservation during the Pennsylvania Firefly Festival and interdisciplinary community programming on fireflies in art and culture will bring the science and impact of insects to the public.
In nature, mating signals are diverse and even closely-related species can employ strikingly different signaling strategies. To understand what generates this diversity, we must understand the fundamental mechanisms and evolutionary processes that govern signal mode change across taxa. Fireflies, in the beetle family Lampyridae, are renowned for their nocturnal light signals that function primarily in mate recognition and choice. While the larvae of all firefly species emit light, only some species emit light as adults. These “unlighted†adult fireflies are diurnal and likely use long- and short-distance pheromones to find mates. In North American taxa, the loss of lighted communication and secondary gain of chemical signals appears to have occurred independently several times. These natural replicates facilitate the exploration of the molecular and behavioral changes that accompany an evolutionary switch in primary mating signal mode. (i) Characterization of volatile and cuticular signaling compounds from pairs of closely related species with contrasting signal modes will test whether chemical repertoires diversify in unlighted taxa. (ii) Next generation sequencing will enable examinations of whether chemical repertoire diversification is accompanied by corresponding diversification of chemosensory receptors, and identify convergent pathways for signal mode switching among firefly clades. (iii) Functional characterization studies will directly link chemosensory receptor genes to specific mating pheromone components. Investigating evolutionary signal mode switches in an organismal system with extreme differences in unimodal signals offers a unique opportunity to develop patterns and predictions that advance the study of more complex multimodal signals.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
