Distribution of Endosymbiotic Reproductive Manipulators Reflects Invasion Process and Not Reproductive System Polymorphism in the Little Fire Ant <i>Wasmannia auropunctata</i>

Endosymbiotic reproductive manipulators may have drastic effects on the ecological and evolutionary dynamics of their hosts. The prevalence of these endosymbionts reflects both their ability to manipulate their hosts and the history of the host populations. The little fire ant <i>Wasmannia auropunctata</i> displays a polymorphism in both its reproductive system (sexual versus clonal populations) and the invasive status of its populations (associated to a habitat shift). We first screened for the presence of a diverse array of reproductive parasites in sexual and clonal populations of <i>W. auropunctata</i>, as a means to investigate the role of endosymbionts in reproductive phenotypes. <i>Wolbachia</i> was the only symbiont found and we then focused on its worldwide distribution and diversity in natural populations of <i>W. auropunctata</i>. Using a multilocus scheme, we further characterized the <i>Wolbachia</i> strains present in these populations. We found that almost all the native sexual populations and only a few clonal populations are infected by <i>Wolbachia</i>. The presence of similar <i>Wolbachia</i> strains in both sexual and clonal populations indicates that they are probably not the cause of the reproductive system polymorphism. The observed pattern seems rather associated to the invasion process of <i>W. auropunctata</i>. In particular, the observed loss of <i>Wolbachia</i> in clonal populations, that recurrently emerged from sexual populations, likely resulted from natural heat treatment and/or relaxed selection during the shift in habitat associated to the invasion process.