Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/1998
Publication Date: N/A
Citation: Interpretive Summary: Several microorganisms cause significant mortality in fire ants in South America and are being evaluated as potential biological control agents of imported fire ants in the United States. Light-microscopic and ultrastructural studies cannot differentiate microsporidian pathogens of the genus Thelohania found in two different fire ant species. In this study we examined molecular characteristics of the pathogens to determine their taxonomic relationships. Sequences of the 16SrRNA gene of Thelohania solenopsae, Thelohania sp. and Vairimorpha sp., three microsporidia pathogenic to the fire ants, Solenopsis invicta and S. richteri, were determined and compared to each other and 15 other species of microsporidia. The results support morphological evidence that T. solenopsae and Thelohania sp. are the same species and that Vairimorpha sp. belongs to a different genus. This information is necessary for designing a biological control strategy for imported fire ants in the United States utilizing these important natural control agents.
Technical Abstract: Sequences of the 16SrRNA gene of three microsporidia pathogenic to imported fire ants, Solenopsis invicta and S. richteri, were determined and compared to each other and 16 other species of microsporidia. The sequences of two Thelohania species are nearly identical (99.2% identity), supporting light-microscopic and ultrastructural evidence that T. solenopsae and Thelohania sp. are conspecific. Sequence comparisons further revealed that Vairimorpha sp. has a sequence identity of about 73% with the two Thelohania species and V. necatrix, the type species of the genus Vairimorpha. This, together with information on spore morphology, suggests that Vairimorpha sp. represents a genus distinct from the fire ant Thelohania. Its placement in the genus Vairimorpha must also be re-evaluated. Two new sister taxa, one containing Thelohania solenopsae, and one containing Vairmorpha sp. were found to have diverged early in the microsporidian lineage.