A ten-year comparative study of the population dynamics and parasitoidism in the native paper wasp Polistes fuscatus and the invasive P. dominulus

The invasive success of Polistes dominulus in North America has been attributed to its greater productivity relative to native Polistes. Liberation from parasites and parasitoids are thought to be major factors contributing to the high productivity of P. dominulus. We analyzed historical records of colony relative abundance and productivity of P. dominulus and the sympatric, native Polistes fuscatus from 1995 to 2010 using historical data from our Michigan Polistes study site. We also analyzed evidence of parasitoids from 294 P. fuscatus and 507 P. dominulus archived combs from 2001 to 2010. Additionally, we examined field and laboratory colonies from outside of our study site for parasites and parasitoids in 2009 and 2010. We documented one parasite and three parasitoids exploiting Polistes in our Michigan study sites. Our historical records document that P. dominulus initially displaced P. fuscatus rapidly, then slowed, and finally the two populations stabilized. Furthermore, the historical pattern of decreasing displacement of P. fuscatus by P. dominulus corresponded temporally with a significant decline in the productivity and a significant increase in Dibrachys cavus infestation of P. dominulus. Our evidence indicates that the parasitoid, D. cavus, is a major factor in stabilizing the populations of the sympatric P. dominulus and P. fuscatus.