Collective offspring-parent signaling in a social treehopper: mechanisms, patterns and function

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] I investigated the properties of collective behavior in a group-living insect, including the patterns of group behavior, the function of group level patterns, and how collective behavior emerges from individual actions. In the treehopper Umbonia crassicornis, offspring live in cylindrical aggregations along a host plant stem. In the presence of a predator, offspring produce synchronized vibrational signals that elicit maternal defense.The mother must approach the predator to defend her offspring, and I found that the collective signals reveal not only the predator's presence, but also its location. I then demonstrated experimentally that defending mothers use information in offspring signals to locate the predator. Finally, I and my collaborators developed an individual-based model of collective antipredator signaling. In the model, individuals contacted by the predator initiate signaling, while other individuals use both local cues (from immediate neighbors) and global cues (from all other group members) to decide whether and when to signal. The model results closely match multiple system-level patterns of offspring communicative networks, and provide insight into the mechanisms by which offspring groups can effectively increase the perceptual range of the defending mother.