The harvester ant genus Pogonomyrmex contains about 60 described species which live moslty in arid or semiarid regions of South- and North America. All species so far analysed are highly polyandrous. P. badius a species from the eastern USA has for example one of the most extreme numerical and effective mating frequencies described for ants. Species in the genus Pogonomyrmex differ considerably in their reproductive mode, sexual dimorphism, sex specific characters and the behavior of queens and males. To understand the evolution of these reproductive traits we established a molecular phylogeny of the genus Pogonomyrmex that contains about 90% of the North American and 30% of the South American species including all Subgenera. Additionally, we try to understand the interaction between different traits involved in reproduction like ovariol number and gyny or mating frequency and male accessory gland size.