The aim of this study is to characterize the means by which reproductive isolation was achieved and is maintained between the three inquiline species within the socially parasitic genus Doronomyrmex Kutter (D. kutteri, Buschinger; D. pacis, Kutter and D. goesswaldi, Kutter). This group of ants is thought to form a monophyletic group (Baur et al. 1995) and species combinations occur in sympatry over a wide area of their distribution range, but also syntope within the same host population (see Fig. 1). Sympatric speciation has long been hypothesized for inquiline (workerless) social parasites like the species of the genus Doronomyrmex. Data on sympatric speciation in diverse taxa accumulate recently and Wolbachia has been detected as a prime mediator in this process. As hyperinfections of different Wolbachia strains have been detected in Doronomyrmex-species and preliminary crossing experiments have shown that gametic isolation takes place, this genus is a prime candidate to test radiation via sympatric speciation for the first time in ants. Observations of mating behaviour and censuses of the offspring resulting from all possible crossings between species and between Wolbachia-infected and uninfected partners should clarify if Doronomyrmex radiated by sympatric speciation and if Wolbachia among others might act as a speciation agent, by inducing cytoplasmatic incompatability.
