Selenium In The Ant Diet: Detection and Impact of Selenate on Argentine Ant (Linepithema humile) Mortality
Deborah De La Riva, Greg Kund, and John T. Trumble
University of California, Department of Entomology, Riverside, CA
Ants serve as a keystone species influencing diversity in many communities. Many ants provide defensive and pollination services for plants by feeding on pollen, floral nectar, extrafloral nectar, seeds and consuming plant pests. Selenium (Se) is a naturally occurring metalloid normally present in low concentrations in the environment. Although Se is an essential element of many plants and animals, this element can become toxic at higher levels. Even among plants that are not considered Se accumulators, selenium has been found in significant levels in many of the structures ants feed upon. The majority of studies investigating selenium toxicity in wildlife have been conducted on livestock and other vertebrates, but relatively few studies have investigated the effects of selenium on insects. Even fewer reports are available for ants. We report here the first of several studies designed to investigate the impacts of Se (as selenate) on toxicity, ant behavior, pollination services and colony structure. Dose-response tests of the ingestion of selenate on the mortality of Argentine ants, Linepithema humile, indicated levels found in the pollen and nectar of radish plants grown in low to moderate concentrations of Se were toxic. Choice tests with selenate-spiked sucrose solutions documented that the ants cannot detect even lethal concentrations of selenate in their diet. We report on the findings of these experiments and discuss their potential ecological implications.