YEAST BIOTA OF THE RED IMPORTED FIRE ANT

Few researchers have addressed the relationship between the Solenopsis complex and its infernal microbiota. Most investigations on the red i mported fire ant (Solenopsis invicta) are either control oriented or e mphasize the species' negative impact on ecosystems. The objectives of this study were to isolate and identify yeasts from the red imported fire ant and to determine the impact of associated yeasts on colony vi gour. Colonies were collected from five locations in Texas that repres ent a transect along a decreasing moisture gradient from the southeast ern to the northwestern region of the state. Colonies were collected d uring winter of 1992, and the spring, summer, and autumn months of 199 3. Physiological and morphological tests showed that the 327 yeast iso lates from worker haemolymph represent five yeast species: Candida par apsilosis, Candida lipolytica, Candida guillermondii, Candida rugosa, and Debaryomyces hansenii var. hansenii. The biomass of red imported f ire ant colonies with yeasts was significantly greater than ant coloni es without yeasts during winter and spring months. Moreover, 80% of th e fourth-instar larvae collected during the autumn months harboured ye asts. These data indicate that the presence of yeast does not reduce c olony biomass. A high prevalence of yeasts in larvae suggests a nutrit ional role and that this association is not random.