Evolutionary reduction of female dispersal in Cataglyphis desert ants

Sexual activity is only a brief moment in the life of ant colonies, but it determines several characteristics of life history. Mating behaviour, distance of female dispersal and mode of colony foundation are interlinked. In species exhibiting ‘male aggregation’ (males and queens fly and mate away from natal nests), newly mated queens have no option but to found a colony alone (independent colony founding, ICF). In contrast, in ‘female calling’ species, queens mate close to the natal nests, then either fly or walk away for dispersal. In several species, they can also disperse on foot accompanied by nestmate workers (dependent colony founding, DCF). Here, we review field observations and genetic data to untangle dispersal strategies across the genus Cataglyphis. We complement these existing informations with queen thorax morphology and dissection of wing muscles. Our comparative study includes 18 species belonging to six species-groups. We found that female calling occurs across all clades, with only two species showing male aggregation. Although most species have normal flying queens specialized for ICF, species in three out of the six species-groups show DCF. Remarkably, species with DCF evolved short-winged ‘brachypterous’ queens that lack wing muscles. Relative size of their thorax sclerites can be used to predict lack of flight ability. Altogether, these results show a marked deviation from the breeding behaviour typical of most species in subfamily Formicinae. We discuss how reduction of female dispersal may be linked to harsh desert conditions.See Supporting Materia