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United States Department of Agriculture

Agricultural Research Service


item Vander Meer, Robert - Bob
item Alonso, Leeanne

Submitted to: Behavioral Ecology and Sociobiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/26/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: The red imported fire ant is a medical and agricultural pest ant whose colonizing success is due in large part to its highly evolved use of chemicals (pheromones) to communicate and regulate the activities of the colony. Workers from single queen colonies are highly aggressive toward workers of other colonies and to newly mated fire ant queens. Workers from mmultiple queen colonies are not aggressive toward other fire ant workers, but are aggressive toward newly mated queens. Nestmate recognition is very important in protecting the queen(s) from outside intrusions, such as pathogens and parasites; therefore, an understanding of how nestmate recognition works is essential for our understanding of population dynamics and for the successful utilization of biological control agents. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, Florida discovered a new queen produced dpheromone that has a dramatic effect on the recognition of other fire ant workers and newly mated queens. In the absence of the pheromone (the queen dies or is removed) workers quickly become non-aggressive toward other workers and will readily adopt other queens. Once a queen is adopted aggression levels increase again toward other workers and newly mated queens. This mechanism is responsible for territoriality in single queen colonies and for keeping other queens from competing with the colony queen. The adoption of newly mated queens by queenless workers is important to our understanding of fire ant population dynamics, especially as related to insecticide control methods that may kill the queen but not all the workers.

Technical Abstract: Monogyne fire ant colony workers are territorial and are aggressive toward members of other fire ant colonies. In contrast polygyne colony workers are not aggressive toward non-nestmates, presumably due to broader exposure to heritable and environmentally derived nestmate recognition cues (broad template). However, after fire ant mating flights, newly mated queens are heavily preyed upon by workers from existing monogyne and polygyne fire an colonies, thus limiting potential reproductive competition. We discovered that existing monogyne and polygyne queens have a remarkable effect on conspecific recognition. After removal of their colony queen, monogyne worker aggression toward non-nestmate conspecifics quickly drop to merely investigative levels; however, heterospecific recognition/aggression remains high. Queenless monogyne or polygyne worker groups were not aggressive toward newly mated queens. Monogyne queenless worker groups that tadopted a newly mated queen became aggressive again toward non-nestmate workers and newly mated queens. We propose that the powerful effect of fire ant queens on conspecific nestmate recognition is caused by a queen produced recognition primer pheromone that increases the sensitivity of workers to subtle quantitative differences in nestmate recognition cues. This primer pheromone results in the regulation of exogenous reproductive competition in S. invicta and when absent allows queenless workers to readily adopt a new queen. The lack of worker/worker aggression in polygyne populations falls within the overall conspecific recognition primer pheromone and is a result of the broad template. This extraordinary discovery has broad implication regarding monogyne and polygyne colony and population dynamics.

Last Modified: 10/18/2017
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