DISSERTATION RESEARCH: The ecology of divergence in vibrational signals of Enchenopa binotata treehoppers

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The proposed research focuses on a group of closely related plant-feeding insects, Enchenopa binotata treehoppers, to understand better how communication signals contribute to the formation of new species. Environments select for efficient communication, which leads to variation in the communication signals when environments differ. Given that only individuals with compatible communication systems tend to mate with one another, these differences also may lead to reproductive isolation among populations in different environments. Enchenopa are host-specific, a situation where each species associates exclusively with a single species of plant. This is ideal situation since ecological differences are well defined by each host-plant species. Species in the Enchenopa binotata complex differ dramatically in the pitch of male mating signals, with each species imparting a different pitch into the stems of its respective host plant. Preliminary results on the transmission properties of two host plant species shows that the same pitch used by the resident Enchenopa species is the pitch that transmits best in the plant, suggesting each insect species is tuned to its host plant. However, ecological differences between populations involve multiple factors, which underscores the importance of understanding what communicating individuals experience in wild populations. To this end the proposed research integrates multiple components of the environment to better understand the natural context in which Enchenopa binotata treehoppers communicate. Signal transmission properties will be characterized for additional host plant species, and background noise resulting from wind-induced vibrations will also be characterized for each host-plant species. Background noise is important since it can mask signals. Further research then will evaluate the impact of these factors on individuals that receive these signals. As proposed, this research will provide the most thorough evaluation of the role of differences in the environmental context of a group of vibrationally-communicating insect species, and how these differences may lead to variation in signals. Broader Impacts: More broadly, the proposed research provides a novel method for accurately measuring vibrational signals as well as training for undergraduates. Further, the training provided to undergraduates has unique breadth, as much of this research stems from collaborations between biologists and engineers. The educational/research experience will prepare the graduate student and undergraduate assistants for future careers in behavioral biology. Also, the techniques used and hypotheses addressed will contribute to theoretical aspects of ecological divergence and evolution in sympatric populations.