In this project, we aimed to gain a deeper understanding of the mechanisms by which mothers can shape the developmental fate of their offspring.  To do this, we used social paper wasps, Polistes fuscatus, excellent models for studying maternal and social behavior.  These wasps make small colonies initiated by founding queens, devoted mothers who spend weeks defending and feeding their offspring.  Interestingly, not all offspring are equal; those produced early in the season are all female and become workers, who are typically sterile, short-lived, and toil for the colony.  On the other hand, offspring produced later in the season are destined to reproduce rather than work—either as males, or as “gynes”— long-lived wasp princesses who will become the next generation of queens.

How do wasps produce such unequal daughters? We used the striking variation in P. fuscatus female developmental fate into different castes (workers or gynes) to study the role of maternal interactions in shaping offspring traits.  We found that there are thousands of genes showing different activity between developing workers and gynes, setting them up for possessing vastly different adult physiology and behavior. Further experiments revealed queen mom’s behavior toward her developing larvae has a profound effect in two important ways.  First, there is food.  Early season larvae are underfed by mom and typically become workers.  We found that restricted feeding alone can lead to the suppression of gyne-related genes, sending larvae on a developmental track to become workers.  Second, how mom interacts with larvae is also key.  Intriguingly, founding queens target vibrational signals at their larvae, called “antennal drumming”.  Previous work suggested these maternal signals lead daughters to become leaner, a worker-like trait.  We designed small “piezoelectric devices” that vibrate nests at mom’s frequency, and attached them to wasp nests in the field.  We found that these vibrations can also influence gene activity during development.  Some gyne-related genes are also shut down by vibrations, while others were influenced by the combination of low food and vibrations.  Thus, both nutritional and tactile maternal influences, and their interaction, work together to influence the caste fate of offspring.

These data provide new insights into how the maternal social environment can influence gene activity in developing offspring.  Importantly, these differences in gene activity have the potential to set up different life trajectories for offspring, leading to adults with vastly different physiology and behavior.  

Last Modified: 08/09/2016
Modified by: Amy Toth