Developmental and Geographical Variation in the Chemical Defense of the Walkingstick Insect Anisomorpha buprestoides
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Anisomorpha buprestoides, a walkingstick common in the southeastern United States, sprays chemicals that irritate and repel threatening insects, birds, or mammals. The active chemical in this substance was initially identified as a monoterpene dialdehyde. This compound can be present in several stereoisomeric forms, and subsequent studies have revealed that A. buprestoides produces at least three diastereomers: anisomorphal, dolichodial, and peruphasmal. However, no inquiry has been made to date into the geographical or developmental dependence of this variation. We report here that different populations of adult A. buprestoides spray either anisomorphal, or peruphasmal, or a mixture of the two stereoisomers. Additionally, offspring of a peruphasmal-producing population produced a variable mixture of anisomorphal and dolichodial but switched to peruphasmal upon reaching sexual maturity. This appears to be the first report of a developmentally regulated change in walkingstick insect chemical defense. Our results suggest a more complex role of these substances in the overall chemical ecology of walkingstick insects.
KeywordsInsect Anisomorpha buprestoides Phasmatodea Development Chemical ecology Monoterpene Anisomorphal Peruphasmal Dolichodial
We thank Drs. W. Brey (NHMFL), R. Withers (Varian), R. Nast (Varian), and Bruker for the 1-mm HTS NMR probe. J. Rocca (AMRIS) provided help with NMR, and O. Conle (Bolsterlang, Germany) provided advice on walkingsticks. Dr. P. Teal (USDA) provided support and laboratory resources. Dr. Omjoy Ganesh (UF) provided technical help with making ternary diagrams. Drs. P. Sternberg (Caltech) and S. Benner (The Westheimer Institute of Science and Technology) provided helpful comments on the text. Funding was from the Human Frontiers Science Program and the NSF funded National High Magnetic Field Laboratory. The authors declare no competing financial interests.
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