Prevalence and Genetic Diversity of a Microsporidian Parasite in the Black Imported Fire Ant and its Social Parasitic Ant (Formicidae: Myrmicinae: Solenopsis) in Buenos Aires Province, Argentina

Authors: Ascunce, Marina; KASSU, GEBREYES - University Of Florida; BOUWMA, ANDREW - Oregon State University; Oi, David; REED, DAVID - University Of Florida; BRIANO, JUAN - Fuedei; SHOEMAKER, DEWAYNE - University Of Tennessee

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2023
Publication Date: 11/21/2023
Citation: Ascunce, M.S., Kassu, G., Bouwma, A., Oi, D.H., Reed, D.L., Briano, J., Shoemaker, D. 2023. Prevalence and Genetic Diversity of a Microsporidian Parasite in the Black Imported Fire Ant and its Social Parasitic Ant (Formicidae: Myrmicinae: Solenopsis) in Buenos Aires Province, Argentina. Insects. 14(12):901. https://doi.org/10.3390/insects14120901.
DOI: https://doi.org/10.3390/insects14120901

Interpretive Summary: The Black Imported Fire Ant, Solenopsis richteri, was accidentally introduced to the southern U.S. in the 1930s from South America. Long-term, sustained suppression approaches through biological control are needed to control these growing fire ant invasive populations. Among those natural enemies used in the U.S., there have been releases of a fungal-like microsporidian pathogen, Kneallhazia solenopsae. Thus, in this study, researchers characterized the prevalence and genetic diversity of this microsporidium in natural populations of Solenopsis richteri. The goal of these type of studies is to assess how the natural enemy acts in the native environment that gained information can be used to improve biological control methods. The researchers analyzed ants from 219 nests and found that in 12.8% of those nests the microsporidium was present. Interestingly, within those S. richteri colonies, researchers found a social parasitic ant, Solenopsis daguerrei, and when those ants were analyzed, 3.9% of S. daguerrei ants tested positive for the microsporidium. Genetically, the microsporidian variants found among both Solenopsis species were the same. Further studies are needed to evaluate the pathogenicity of this microsporidian variant.

Technical Abstract: Microsporidia are natural pathogens of arthropods and have been used as biological control against insect pests. In the United States, efforts to control the invasive Red Imported Fire Ant, Solenopsis invicta, and Black Imported Fire Ant, Solenopsis richteri, have included the use of the microsporid-ium, Kneallhazia solenopsae. However, there is limited information about the genetic differences between the microsporidian variants found in S. invicta and in S. richteri. In this study, we assessed the prevalence and genetic diversity of K. solenopsae in S. richteri from South America. Additionally, we examined the social parasitic ant, Solenopsis daguerrei, found in some S. richteri nests. The survey of 219 S. richteri nests revealed K. solenopsae infections in all 5 sites analyzed, with 28 colonies (12.8%) positive for the microsporidium. Among 180 S. daguerrei, 7 ants (3.9%) tested positive for K. solenopsae in 3 sites. Phylogenetic analyses of the microsporidian variants infecting S. richteri and S. daguerrei based on sequences from the 16S ribosomal RNA gene showed that both ant species shared the same microsporidian variant, which is different from the ones found in S. invicta. Further studies are needed to determine the pathogenicity of genetically different K. solenopsae variants among Solenopsis species.