Insecticides reduce survival and the expression of traits associated with carnivory of carnivorous plants
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While agrochemical pollution is thought to be an important conservation threat to carnivorous plants, the effects of insecticides on these taxa have not been quantified previously. Using a combination of lab- and field-based experiments, we tested the effects of commercial and technical grades of three widely used insecticides (carbaryl, lambda-cyhalothrin, and malathion) on survival and the expression of traits associated with carnivory of pink sundews (Drosera capillaris) and Venus flytraps (Dionaea muscipula). Commercial grades were generally more harmful than technical grades under lab and field conditions, but all three insecticides were capable of reducing both survival and the expression of traits associated with carnivory within recommended application rates. However, pink sundews appeared to be more susceptible to insecticides than Venus flytraps, perhaps because of larger numbers of digestive glands on the leaf surfaces. We make several recommendations for future research directions, such as examining the long-term effects of insecticides on carnivorous plant populations, for example in terms of growth rates and fitness. Additionally, future research should include representative species from a wider-range of carnivorous plant growth forms, and explore the mechanism by which insecticides are harming the plants. Given the effects we observed in the present study, we suggest that the use of insecticides should be carefully managed in areas containing vulnerable carnivorous plant species.
KeywordsCarnivorous plants Conservation Dionaea muscipula Drosera capillaris Insecticides
This work was supported in part by a Fern Garden Club Scholarship, and Rutlish Foundation Grant to D.E.J., and University of South Florida Office of Research and Innovation New Researcher (RO65462), and US Department of Agriculture (USDA: NRI 2006-01370, 2009-35102-0543) grants to J.R.R. We thank Chris Anderson for taking the photographs used in Fig. 2, Amanda Squitieri for assistance with data collection, and members of the Rohr lab and three anonymous reviewers for improving the manuscript.
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