Genetic and social structure of the queen size dimorphic ant Leptothorax cf. andrei

1. The study of queen polymorphisms can provide insight into the evolution of alternative life histories in ants. In this paper, results of morphological, social and genetic investigations of the newly discovered queen size dimorphism in Leptothorax cf. andrei are presented. 2. Queens had a bimodal size distribution, and were classified as large (macrogynes) or small (microgynes) queens. Despite their small size, microgynes had a fully developed external flight apparatus and a functional reproductive tract. 3. Queen morphology was not correlated with colony social structure, and the relatedness among nestmate queens was high, indicating secondary polygyny by re‐adoption of related queens (daughters) into existing colonies. 4. The distribution of microsatellite alleles indicated that there is a genetic separation between macro‐ and micro‐gynes but the two morphs belong to the same species. 5. The results support the hypothesis that microgyny in Leptothorax has not evolved as a specialisation to inter‐ or intra‐specific social parasitism but rather is an adaptation to alternative dispersal behaviour.