Alternative reproductive tactics in the queen-size-dimorphic ant Leptothorax rugatulus (Emery) and their consequences for genetic population structure

We report the results of a comprehensive investigation of the queen size di morphism in the North American ant Leptothorax rugatulus. Employing allozym es and microsatellites as genetic markers, we found no evidence that the ge ne pools of large (macrogynes) and small (microgynes) queens are distinct. Queens in polygynous colonies are related to each other, supporting the hyp othesis that colonies with more than one queen commonly arise by the adopti on of daughter queens into their natal colonies. The higher fat content of macrogynes, their predominance in monogynous societies and in small foundin g colonies, and their greater flight activity favor the view that macrogyne s predominantly found colonies independently, while microgynes are speciali zed for dependent colony founding by readoption. When comparing the genetic structure of three different subpopulations, we found that the alternative life histories had no significant effect on population viscosity at the sc ale investigated.