JSD Departmental Seminar


“The role of conspecific odor in the formation and traditional location of overwintering aggregations of convergent ladybird beetles (Hippodamia convergens)”
Christopher Wheeler
Ph.D. Candidate, Dept. of Biology, UCR
From: 11:00 AM To: 12:00 PM
Thursday, Feb 17, 2011
Burns Lecture Hall, Keck Science Center
The convergent ladybird beetle (Hippodamia convergens), an important biological control agent for aphids and mites, seasonally migrates from lowland foraging habitats to mountain-top aggregations to overwinter. These aggregations recur in the same sheltered hibernacula as those frequented by previous generations of migrants. Others have suggested that the permanence of these hibernacula is due to the ability of H. convergens to orient towards pheromone cues from conspecifics. We test this hypothesis with a series of olfactometer bioassays that examine the orientation of H. convergens adults exposed to conspecific headspace odors. Gas chromatography-mass spectrometry (GC-MS) is being used to characterize the volatiles emitted by individuals and aggregations. The behavioral significance of these chemical constituents will be tested with coupled gas chromatography-electroantennogram detection (GC-EAD) and additional bioassays. In still-air olfactometer bioassays, H. convergens show significant preference for volatile odors derived from aggregations of conspecifics. Additionally, these bioassays show that a synthetic equivalent of a pyrazine found in the beetles’ headspace, may play an important role in the localization of aggregations. This pyrazine, 2-isopropyl-3-methoxypyrazine, is responsible for the characteristic odor of many coccinellids and is an established alerting odor in this and other aposematic species. The parsimonious role of this alerting defensive odor is discussed in the context of the evolution of aposematic signaling, distastefulness, and the costs and benefits of aggregations.
Seminar Registered by: Boyle Ke


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