Many highly social species show plasticity in their social structure in response to different environmental conditions. For example, typical colonies of the yellowjacket wasp Vespula squamosa are headed by a single reproductive queen and survive for only a single season. However, in warmer climates, V. squamosa colonies sometimes persist for multiple years and can grow to extremely large size. We used genetic markers to understand patterns of reproduction and recruitment within these perennial colonies. We genotyped V. squamosa workers, pre-reproductive queens, and males from perennial colonies in the southeastern United States at 10 polymorphic microsatellite loci and one mitochondrial DNA locus. We found that V. squamosa from perennial nests were produced by multiple reproductives, in contrast to typical annual colonies. Relatedness of nestmates from perennial colonies was significantly lower than relatedness of nestmates from annual colonies. Our analyses of mitochondrial DNA indicated that most V. squamosa perennial colonies represented semi-closed systems whereby all individuals belonged to a single matriline despite the presence of multiple reproductive females. However, new queens recruited into perennial colonies apparently mated with non-nestmate males. Notably, perennial and annual colonies did not show significant genetic differences, supporting the hypothesis that perennial colony formation represents an instance of social phenotypic plasticity. Overall, our results indicate that perennial V. squamosa colonies show substantial changes to their social biology compared to typical annual colonies.

PCRs were used to amplify DNA at 10 microsatellite loci. PCRs were generally conducted in a final volume of 15 μL composed of: 6.4 μL deionized water, 2.4 μL 25mM MgCl2, 1.5 μL 10x PCR buffer, 1.2 μL 2.5mM dNTPs, 1 μL Taq polymerase, 0.75 μL each of 10 μM reverse and fluorescence-tagged forward primers, and 1 μL of DNA. The PCR amplification profile used for each locus was: 2 min at 94°C, 35 cycles for 30 sec at 94°C, 30 sec at locus-specific annealing temperature (Table 2), 30 sec at 72°C, and then a final extension for 5.5 min at 72°C. PCR products were run on a 3% agarose gel at 100V to verify amplification for each individual.

After confirmation of amplification, microsatellite genotypes were analyzed using the fragment analysis module of an ABI 3100 sequencer. Scoring was completed using a combination of GeneMapper v4.0 (Applied Biosystems, Foster City, CA) and manual scoring of peaks.

Data are in Genepop format (i.e. 185/189 -> 185189). Haploid males are represented as diploid with their allele doubled (i.e. 185 -> 185185).