| Few investigations have examined the relationship between Solenopsis complex and its internal microflora. Most investigations on the red imported fire ant are either control oriented or emphasize the species' negative impact on ecosystems. Therefore, the objectives of this research were (1) to isolate and identify yeasts from the red imported fire ant, (Solenopsis invicta), (2) to determine the impact of associated yeasts on red imported fire ant colony vigor, and (3) to clarify the significance of the association by obtaining and comparing sterol profiles of the yeast flora and the red imported fire ant.; Colonies were collected from five locations in Texas: Beaumont, Huntsville, Waco, Stephenville, and Abilene. These sites represent a transect along a decreasing moisture gradient from the southeastern to the northwestern region of the state. Colonies were randomly collected during winter of 1992, and the spring, summer, and fall months of 1993. Physiological and morphological tests showed that the 327 yeast isolates from Solenopsis invicta haemolymph represent five yeast species: Candida parapsilosis (168 isolates), Candida lipolytica (123 isolates), Candida guillermondii (18 isolates), Candida rugosa (9 isolates), and Debaryomyces var. hansenii (9).; Using GLM statistical procedures, the biomass of red imported fire ant colonies with yeasts was significantly greater (P {dollar}<{dollar} 0.005) than ant colonies without yeasts during winter and spring months. A significantly greater (P {dollar}<{dollar} 0.005) colony biomass was observed for fire ant colonies collected only from the Abilene site. This response was site specific. Moreover, 80.3% of the fourth instar larvae collected from Beaumont, Huntsville, Waco, and Abilene collected during the fall months, harbored yeasts. These data indicate that the presence of yeast does not have a negative impact on colony vigor. A high prevalence of yeasts in larvae suggests a nutritional role.; The fact that the fungal sterol, ergosterol, was detected in worker larvae, adult workers, and eggs suggests that these yeast symbionts may contribute to the sterol pool of the red imported fire ant. These data suggest that this association is not random, and a highly selective process is taking place between the yeasts and the fourth instar larva. Consequently, this association may yield novel approaches in red imported fire ant control if behavioral parameters of the ant are considered in the development and application of microbial control agents. In addition, means of yeast colony forming units per gram of soil between mound soil and soil adjacent to mounds were significantly different (P {dollar}<{dollar} 0.001). Also, nutrient concentration such as phosphorus in soil from brood chamber was significantly greater than control samples (P {dollar}<{dollar} 0.05). |
