Abstract
Insect diversity and biomass have been declining around the world. This might have severe consequences on the environment since insects provide many crucial ecosystem services. One major driver behind the decline is continuous pesticide use which also affects nontarget organisms. Even at low doses, chronic exposure to pesticides may have negative long-term effects. Ants have not received much ...
Abstract
Insect diversity and biomass have been declining around the world. This might have severe consequences on the environment since insects provide many crucial ecosystem services. One major driver behind the decline is continuous pesticide use which also affects nontarget organisms. Even at low doses, chronic exposure to pesticides may have negative long-term effects. Ants have not received much attention in this context, despite their importance in terrestrial ecosystems. A full factorial experimental design was used to test how ingestion of two widely used pesticides influence colonies of the ant Cardiocondyla obscurior. Colonies were exposed for 12 weeks to the herbicide glyphosate and the neonicotinoid insecticide thiacloprid, separately and in combination. Brood production and the size of new workers and queens produced in these colonies were measured. In addition, the relative densities of two endosymbionts were quantified and immunocompetence tested by measuring survival after fungal infection. The two pesticides in combination decreased brood production, which was measured as the number of produced eggs and pupae. Workers and queens produced in pesticide-exposed colonies differed in body size from individuals produced in control colonies. Furthermore, endosymbiont densities decreased after glyphosate exposure. Neither pesticide influenced survival after fungal infection. The results show that chronic exposure to two widely used pesticides causes apparent trade-offs in reproduction and other physiological traits of ants, potentially decreasing fitness. Even low levels of pesticides in the environment may therefore have negative effects on ant colonies, contributing to the worldwide insect decline.
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