title: Living on the edge: populations of two zooplankton species living closer to agricultural fields are more resistant to a common insecticide.
abstract: Ecological communities across the globe are exposed to diverse natural and anthropogenic stressors and disturbances that can lead to community-wide impacts. Contaminants are a group of anthropogenic disturbances that are ubiquitous in the environment and can trigger trophic cascades, increased susceptibility to pathogens, reduced biodiversity, and altered ecosystems. In these ecosystems, substantial attention has been given to evolved resistance in targeted pest species, but little attention has been given to the evolution of resistance in nontarget species in nature. For the present study, the authors used laboratory toxicity tests to determine if 2 common, co-occurring species of freshwater zooplankton (Simocephalus vetulus and Daphnia pulex) showed population-level variation in sensitivity to a common insecticide (chlorpyrifos). For both species, it was found that populations living near agricultural fields--a proxy for pesticide use--were more resistant to chlorpyrifos than populations collected from ponds far from agriculture. This finding is consistent with the evolution of resistance to pesticides. To the authors' knowledge, only 1 previous study (using Daphnia magna) has demonstrated this relationship. Collectively, these results suggest that evolved resistance may be common in zooplankton populations located near agriculture. Moreover, because zooplankton play a key role in aquatic food webs, it is expected that population variation in resistance would dramatically alter aquatic food webs, particularly with exposure to low concentrations of insecticides.
authors.affiliation: Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Randall J
authors.initials: RJ
authors.lastname: Bendis
authors.forename: Rick A
authors.initials: RA
authors.lastname: Relyea
mesh_terms: D000383:Agriculture; D000818:Animals; D004390:Chlorpyrifos / Q000633:toxicity; D003445:Crustacea / Q000187:drug effects; D003621:Daphnia / Q000187:drug effects; D005618:Fresh Water / Q000737:chemistry; D007306:Insecticides / Q000737:chemistry / Q000633:toxicity*; D007928:Lethal Dose 50; D015048:Zooplankton / Q000187:drug effects*
chemical_list: D007306:Insecticides; D004390:Chlorpyrifos
keywords: Biocide; Cladocerans; Median lethal concentration (LC50); Sensitivity; Toxicology