Ant Community Composition in a citrus grove reveals eastern expansion in Florida of the South American big-headed ant, Pheidole obscurithorax Naves (1985)

Authors: Ascunce, Marina; Porter, Sanford; CARROLL, KATHERINE - University Of Florida; PEREZ, PATRICIA - University Of Florida; Nisip, Andrew; AUFMUTH, JOE - University Of Florida; Justice, Lauren; GAVILANEZ-SLONE, JENNY - University Of Florida; QURESHI, JAWWAD - University Of Florida; LUCKY, ANDREA - University Of Florida

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2023
Publication Date: 3/29/2024
Citation: Ascunce, M.S., Porter, S.D., Carroll, K.C., Perez, P., Nisip, A.J., Aufmuth, J., Justice, L.M., Gavilanez-Slone, J.M., Qureshi, J.A., Lucky, A. 2024. Ant Community Composition in a citrus grove reveals eastern expansion in Florida of the South American big-headed ant, Pheidole obscurithorax Naves (1985). Florida Entomologist. 107(1). https://doi.org/10.1515/flaent-2024-0011.
DOI: https://doi.org/10.1515/flaent-2024-0011

Interpretive Summary: Due to human global trade, many species have been transported outside of their native range and introduced to new areas where they became established. Introduced species that have a negative or potentially negative impact on the environment, the economy, or human health are considered to be invasive species or invaders. Invasive species displace native fauna, reduce biodiversity, impair ecosystem services, serve as pathogen vectors, and act as pathogens themselves. Florida is home of several invasive species, including invasive ants. In this study, we assess the impact of one of the worst invasive ants worldwide, the Red Imported Fire Ant, Solenopsis invicta, in a citrus grove ant community. During the summer of 2018, we sampled ants using pitfall traps, which allow us to collect ants as the fall in the trap put in the soil. We delineated 3 transects separated by 25 meters, within each transect, we placed 7 to 10 pitfall traps at 5 meters intervals, leading to a total of 25 pitfall traps. Traps were collected after 48 hours, ants were sorted and identified. RIFA was present in all the traps (100%), while 19 traps (76%) had Dorymyrmex bureni (Trager), the pyramid ant, which is native to the Southeast US. Two tramp species: Cardiocondyla emeryi (Forel) and Brachymyrmex obscurior (Forel) were found in 15 (60%) and 11 (44%) traps, respectively. The South American big-headed ant, Pheidole obscurithorax (Naves), was found in 14 traps (56%), this species is thought to successfully compete and/or co-exist with RIFA and to our knowledge, this is the first report of species in this eastern part of peninsular Florida. Our study highlights the continued spread of introduced and invasive ants in Florida, as well as the erosion of native ant diversity in this citrus grove probably due to in part to invasive ants.

Technical Abstract: Florida has become a worldwide hot spot for introduced and invasive ants (Hymenoptera: Formicidae) including five of the worst invasive ants, such as the Red Imported Fire Ant (RIFA), Solenopsis invicta (Buren). Another invasive insect in Florida is the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), that is the vector of Candidatus Liberibacter asiaticus (CLas), the causal pathogen of citrus greening, the worst citrus disease in the world. Because ACP establishes beneficial interactions with invasive, introduced and native ants in Florida, in this study, we measured the ant diversity in a citrus grove in south Florida, as a first step to assess potential ant-ACP interactions in future studies. During the summer of 2018, 25 pitfall traps were set in a citrus grove. RIFA was present in all the traps (100%), while 19 traps (76%) had Dorymyrmex bureni (Trager), the pyramid ant, which is native to the Southeast US. Two tramp species: Cardiocondyla emeryi (Forel) and Brachymyrmex obscurior (Forel) were found in 15 (60%) and 11 (44%) traps, respectively. The South American big-headed ant, Pheidole obscurithorax (Naves), was found in 14 traps (56%), this species is thought to successfully compete and/or co-exist with RIFA and to our knowledge, this is the first report of species in this eastern part of peninsular Florida. Finally, Cardiocondyla venustula (Wheeler), an introduced ant from the Old World, was found in one of the pitfalls. Although, this ant is found in South Florida, it seems less common, and this is its first report in this region of Florida. Our study highlights the continued spread of introduced and invasive ants in Florida, as well as the erosion of native ant diversity in this citrus grove most likely as a result of the “invasional meltdown” process and management practices.