DISSERTATION RESEARCH: Inducible egg stacking defends against parasitism in a seed beetle

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A broad range of organisms appears able to predict the harshness of future environments and to change the quality of their offspring accordingly. This project focuses on a common beetle that lays stacks of two eggs in order to protect the lower egg from an egg parasitoid and to increase its survival.. Top eggs have reduced mass relative to bottom eggs, and do not complete development, even in the absnce of parasitism. While stacking eggs improves the quality of the bottom-most eggs, it requires more resources and therefore decreases the number of offspring that can be produced. Female beetles anticipate this tradeoff by reducing the nutrients allocated to the sacrificial (top) eggs before they are laid, but the cues eliciting nutrient reallocation and stacking behavior are currently unknown. The researchers will initiate a series of experiments to determine the specific environmental cues responsible for stacking behavior and the sensitivity of female beetles to these cues. They predict that both chemical and volatile cues from the parasitoid cause the stacking response; and that beetles adjust the number of stacks they produce in response to parasitoid density.The beetle-wasp interaction system offers special opportunities for communicating the excitement of scientific discovery to young people. The research has been used in K-12 classes and public settings to illustrate insect diversity and to teach ecological interactions such as herbivory and parasitism. Over the course of the project, outreach using this interspecific interaction will be continued through an elementary and middle school outreach program at the University of Arizona, Insect Discovery. In addition, undergraduate students recruited from under-served groups in biology will participate in the project.