Prevalence of a microsporidian parasite in different social forms of the red imported fire ant, Solenopsis invicta, in its native range in Argentina

We surveyed 559 colonies of the fire ant Solenopsis invicta in 15 sites in its native range in Argentina for the microsporidian parasite Kneallhazia solenopsae, a natural enemy of this ant. The microsporidium was detected in 20 out of 508 monogyne and nine out of 51 polygyne colonies corresponding to mean infection prevalences of 3.31% and 13.68%, respectively. In the USA, previous studies have shown that K. solenopsae prevalence in the polygyne social form is variable, and as high as 100% in certain sites, whereas infections in the monogyne social form in the USA are rare. In this study, we found that the K. solenopsae genetic variant in the USA is genetically different from the variants identified in the native range, supporting the idea that the USA variant may only infect polygyne colonies.