Comparative genomic analyses reveal population structure associated with variable climate in a widely distributed social wasp

Although many species have wide geographic distributions, each distinct population may adapt to their local environment. Evidence of population genetic structure closely linked to variable environmental conditions is consistent with local adaptation. However, other evolutionary processes such as limited gene flow, dispersal constraints and habitat fragmentation can also influence population structure and result in a pattern of isolation by distance. How do populations adapt to local climatic conditions and seasonal timing? Which genes mediate adaptive responses to clinal variation in the environment? We here take advantage of Mischocyttarus mexicanus cubicula, a primitively eusocial wasp distributed along a climatic gradient from subtropical South Florida to temperate South Carolina in the United States. We report a high-quality genome assembly and use whole genome re-sequencing to test if major climatic transitions in ten populations across the species’ range are correlated with genomic population structure. Our results indicate two genomically distinct populations that clearly follow the transition from subtropical to temperate zones. Further, we test if phenotypic variation across the latitudinal transect follow the predictions of Bergman’s and Allen’s rule for clinal variation in body size and appendage length, respectively. Our study provides novel insights into the evolutionary forces that mediate population structure in M. mexicanus and the foundation to explore candidate genes that facilitate adaptation to clinal variation in climatic conditions.