Biodiversity of fungi in red imported fire ant (Hymenoptera:Formicidae) mounds

Abstract

The red imported fire ant, Solenopsis invicta Buren, became established in North America more than 70 yr ago, and it currently occupies most of the southeastern United States. Fire ants change the physical and chemical components of soil, which likely influence soil fungi in ant mounds. To determine the effects of fire ants on soil fungi, we sampled soil from fire ant mounds and the surrounding nonmound soil. In addition, we sampled soil from the nests of the native ant Aphaenogaster texana carolinensis Wheeler. We found that both fire ant mounds and native ant nests had greater fungal abundance but lower species richness and diversity than nonmound soil. Fire ant mounds contained 19 times more colony forming units (cfu g-1) than adjacent soil; however, nonmound soil had more than twice the number of fungal species. Two species (Papulaspora byssina Hotson and Penicillium janthinellum Biourge) made up the majority (54.5 and 19.2% relative colony frequencies, respectively) of fungi in fire ant mounds. These high proportions of limited numbers of fungal species in fire ant mounds indicate that only some species are tolerant to and thrive in mound conditions. Alternatively, fire ants might not selectively remove these fungi from their mounds. Given the high densities of fire ants and their frequent mound movements, changes in soil fungal communities might have lasting impacts on soil conditions. In addition, we suggest that differences between fungal communities in soil from native and non-native ant colonies might indirectly influence ant-mediated seed dispersal by affecting seedling survival.