Reproductive decisions by colonies of Vespula wasps

Social insect colonies represent fascinating systems in which to investigate resource allocation, because insect societies act both as “superorganisms” and as groups of distinct individuals.  Thus, on the one hand, insect societies appear to function as single organisms attempting to balance investment in growth and reproduction.  On the other hand, social insect colonies are actually collections of distinct individuals with contrasting interests.  Such divergent interests may lead to conflict affecting how colonies ultimately allocate resources towards growth and reproduction.  We investigated allocation decisions in the social wasp Vespula maculifrons to understand how social insects make reproductive choices.  We first determined how colonies apportioned resources to growth and reproduction.  In contrast to expectations, colonies invested in both growth (workers) and reproduction (males) simultaneously.  In addition, colonies reversed their reproductive choices by decreasing investment in males late in the season.  To further investigate reproductive decisions within colonies we determined if the male mates of queens varied in their reproductive success over time.  Sperm use by queens did vary over time suggesting that male success may depend on sperm clumping.  Finally, we tested if colony sex ratio conformed to expectations under kin selection theory that nestmate relatedness would positively correlate with investment in new queens if workers controlled sex allocation.  Surprisingly, the proportion of queens produced by colonies was negatively correlated with nestmate relatedness, suggesting that allocation may be shaped by advantages arising from multiple mating by queens.  Overall, our study suggests that the reproductive decisions of colonies are flexible and may depend both on environmental and genetic cues.