3.1 | Between-nest sharing and colony genetic structure
All treated nests showed elevated \(\delta\)15N values, indicating that our methods were successful in enriching the isotope values of individual nests. Counter to our expectations, treated nests shared very little with neighboring nests, regardless of social form (Fig 2a) and within-nest relatedness between workers (Appendix S5). Five of the 52 untreated nests showed evidence of sharing with the treated nest (two monogyne and three polygyne). Sharing was independent of the social form of the treated nest (χ2 = 0.0091, df = 1, P = 0.924), the social form of the untreated nest (χ2 = 0.0001, df = 1, P = 0.992), and by the interaction between these variables (χ2 = 0.0061, df = 1, P = 0.938). Moreover, sharing was independent of within-nest relatedness between workers in the treated nest (χ2 = 0.0681, df = 1, P = 0.794), by relatedness between workers in the untreated nest (χ2 = 0.7718, df = 1, P = 0.380), and by the interaction between these variables (χ2 = 0.000, df = 1, P = 1.000).
There was a significant effect of distance on whether or not sharing was detected in untreated nests (χ2 = 10.0858, df = 1,P = 0.001). All untreated nests with elevated\(\delta\)15N values were within 5 m of the treated nest (Fig 2b). However, not all nests within 5 m of the treated nest shared (Fig 2b, Appendix S6), indicating that distance was not the only component influencing sharing between nests. There were 13 untreated nests within 5 m from the treated nest that did not share with the treated nest, one of which was only 0.4 m from the treated nest. Sharing between nests did not vary by site (χ2 = 2.0408, df = 5, P = 0.843).
Treated nests were genetically indistinguishable from the untreated nests with which they shared and were likely part of the same polydomous colony. Pairwise F ST values between the treated and untreated nests were significantly lower on average and near zero in nests that shared (mean and standard errors: 0.028 ± 0.015) than in nests that did not share (0.228 ± 0.021; χ2 = 14.5562, df = 1, P < 0.001; Fig 2c). Likewise, all untreated nests that shared were not genetically differentiated from the treated nest according to the log-likelihood (G)-based test of differentiation. Genetic clustering of nests using PCA and STRUCTURE analyses is provided for each site in Appendix S3. There was no significant interaction between distance and pairwise F ST values (χ2 = 0.3395, df = 1, P = 0.560). PairwiseF ST between polygyne nests within each site was lower than between monogyne nests (mean and standard errors of 0.144 ± 0.008 and 0.356 ± 0.010 respectively), but there was no significant interaction between pairwise F ST and social form (χ2 = 0.0000, df = 3, P = 1.000) on sharing between nests. For each site, the number of alleles, as well as observed and expected heterozygosity are provided for each microsatellite marker in Appendix S7.