Genetic characterization of the red imported fire ant (Solenopsis invicta) in Virginia

This study is the first attempt to characterize colony social form and document the presence of potential biological control agents in fire ant colonies located in Virginia. Red imported fire ant (Solenopsis invicta) workers were sampled from 26 colonies found in seven Virginia cities (2007-2008). DNA and RNA were extracted from ten worker ants from each colony. Multiplex PCR was conducted to determine colony social form (monogyne or polygyne) and to detect the presence of biological control agents released in several surrounding states. These agents include the microsporidian parasite, Thelohania solenopsae, and the fire ant decapitating fly, Pseudacteon spp. Additionally, RNA extracted from samples was amplified by RT-PCR to detect the presence of Solenopsis invicta virus (SINV). Multiplex PCR results indicated that 74% of the Virginia sample colonies were polygyne. These results suggest that fire ants in Virginia will be able to rapidly establish and spread within the state. The results from the biological control studies indicated that biological control agents may be naturally occurring in some Virginia fire ant colonies. T. solenopsae was found in eleven colonies. Surprisingly, two colonies were found to have been parasitized by Pseudacteon spp. flies, although the nearest fly release point was over 100 miles away. RT-PCR results indicated that five colonies were naturally infected with SINV. While the documentation of polygynous fire ant colonies in Virginia suggests that these ants will spread rapidly, the presence of naturally acquired and artificially released biological control agents may be able to slow their expansion.