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Impact of selenium in the ant diet on the argentine ant, Linepithema humile (Hymenoptera: Formicidae)
Impact of Selenium In The Ant Diet on the Argentine Ant, Linepithema humile (Hymenoptera: Formicidae)
Deborah De La Riva, Greg Kund, and John T. Trumble
University of California, Department of Entomology, Riverside, CA
Ants serve as keystone species, playing a critical role in insect and plant species richness in many communities via predatory, pollination, and seed dispersal services. Selenium, a naturally occurring metalloid normally present in low concentrations, is an essential element for animals and some plants, but can become toxic at even moderate levels. Among selenium accumulating plants, selenium has been found in significant levels in the seeds, pollen, and nectar, all of which ants feed upon. Dose response tests ranging in concentration from 0-50 ppm on Linepithema humile (Hymenoptera: Formicidae) workers were conducted to compare the toxicity of both inorganic (selenate) and organic (selenomethionine) forms of selenium. Selenate was found to be the most toxic species, although selenomethionine also caused mortality at ecologically relevant concentrations. We also determined whether ants could detect selenium in their diet in choice tests, where ants were given a choice to feed from an uncontaminated sucrose solution or a solution with highest concentration of selenium tested during the dose response assay. Ants were not repelled by lethal concentrations of selenium in choice tests. Because of this, workers have the potential to acquire selenium directly from plant structures or through tri-trophic interactions with plant herbivores, thus posing a problem for other castes in the colony. We will report on the results of these as well as currently running experiments and discuss future directions toward investigating both colony development and the ecological implications following chronic exposure.
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