Population genetics of the widespread social wasp, Polistes metricus reveals genetic variation associated with climate.

Polistes metricus is a primitively eusocial paper wasp found over a broad geographic range throughout the eastern United States. The wide range of environments in which Polistes metricus is found drives the question of how selection and limited gene flow may have acted to differentiate geographically distant populations. We examined genetic differentiation in P. metricus collected throughout the eastern U.S. at 12 highly polymorphic microsatellite DNA loci. Five of the seven loci we used have been recently developed and shown to be linked to coding genes while the other 7 are not known to be linked to coding regions. We found moderate genetic differentiation among sites, and the differences were more pronounced for the loci linked to coding regions, suggesting that selection may operate to maintain genetic differences The computer program Structure found that it was most likely there were 3 distinct populations, however, 1 of these populations was most prominent. The average proportional membership in the majority population vs. the 2 minority populations was strongly related to the average annual temperature and the amount of precipitation in the warmest quarter of the year. Thus, while the genetic differences were relatively small, they appear to be related to ecological variation and suggest local adaptation