Sociogenetic responses to ecological variation in the ant Myrmica punctiventris are context dependent

Models of social evolution predict a strong relationship between ecological factors and sociogenetic organization in social insects (e.g, queen number , nestmate relatedness and population structure). Despite a large body of c oherent theory, empirical support for these predictions is weak. Here we re port the results of an experiment that manipulated two ecological parameter s, food and nestsite availability. thought to be important for a population of the forest ant Myrmica punctiventris. Earlier work had shown that the s ociogenetic structure varies between two populations of this species, and a n ecological experiment in one of the populations (in Vermont) revealed tha t food supplementation had the strongest effects on nestmate relatedness. W e repeated the experiment in the second population (in New York) and obtain ed strikingly different results. We show that nestsite supplementation had the strongest effect in the New York population, and that adding both food and nestsites affected nestmate relatedness in a direction opposite to that reported from the Vermont study. These results show that the ecological co ntext is critically important for understanding the determinants of colony structure in ants. Furthermore, comparison of our data with that of a previ ous study shows that social organization in New York is temporally unstable . Thus, not only do ecological factors strongly influence social organizati on, but their influence can vary over time. Our study underscores the need for detailed information on the natural history and ecology of social speci es.