Nest site limitation and facultative polygyny in the ant Leptothorax longispinosus

Summary

The ant L. longispinosus displays geographic variation in its pattern of facultative polygyny (Fig. 2). In nature, nest density and frequency of multiple queening are positively associated over three sites. A putative causal relation between availability of vacant nest sites and polygyny was examined in New York, where a plot was seeded with additional nest sites and monitored for 24 months. Both queen number and worker number per nest on the experimental plot were reduced relative to controls (Fig. 4, Fig. 5), indicating that scarcity of available nest sites influences the pattern of polygyny in this species. The observed demographic changes resulted from fractionation of existing colonies; adding nest sites induced polydomy. Although numbers of adult ants changed with addition of nest sites, the numbers of immatures were no different after 2 years (Table 1), suggesting that the population was undergoing growth to expand into the additional sites. These results are the first direct experimental evidence linking polygyny to an ecological parameter for any ant species.