Abstract
How social organisation (number of queens and mating partners) and reproductive system (use of thelytoky vs sex) evolved in ants and how they interplay is still far from clear. The Cataglyphis desert ants represent a fascinating group as it harbours variation in both levels of polyandry and the use of thelytoky, with polyandry and sexual reproduction probably being the ancestral state. In this study, we compared the colony and population genetic structure of two populations of the Cataglyphis cursor group distributed in a remote small geographic area in central Spain with two closest geographic species C. piliscapa and C. cursor. We found that the two populations are genetically isolated from C. piliscapa and C. cursor. However, the population genetic diversity was like C. piliscapa and C. cursor. We observed a lower level of polyandry in C. cursor from Spain compared to C. piliscapa and C. cursor. We found no evidence that C. cursor queens from Spain reproduce thelytokously. This supports the hypothesis that thelytoky is disfavored in systems with lower levels of polyandry. The reversion from polyandry towards monandry has rarely been observed in ants. We present multiple hypotheses that could explain this phenomenon. We raise the possibility that these remote populations belong to a putatively new species. However, this requires a careful taxonomic investigation. Our study confirms the lability of the reproductive system in this group and provides an exciting system to investigate the coevolution of polyandry and thelytoky.