Microsatellite DNA markers reveal details of social structure in forest ants

We developed microsatellite loci from the genome of the temperate forest ant Myrmica punctiventris and used them to study colony genetic structure. We report here primer sequences for three new microsatellite loci, and also show that previously published primers isolated from a congener amplify loci in our study species. Successful cross-priming of loci in four other ant species further illustrates that investigators may now be able to sidestep the labour of developing new microsatellite systems. The microsatellite data allowed us to estimate coefficients of relatedness far more precisely than was possible from previous allozyme work. Furthermore, we obtained evidence of complex colony structure in this population: while overall colonies showed a relatedness structure that is consistent with values expected for a single, once-mated queen (Hamilton 1964), some nests contained worker-laid males, while others included members of at least two families. We used these data to examine reproduction as a function of genetic structure, and found evidence of sex ratio compensation in this species: nests containing worker-laid males allocated more energy to reproduction and had strongly male-biased allocation ratios relative to others in the population.