Inducible pesticide tolerance in Daphnia pulex influenced by resource availability

Abstract

Pesticides are a ubiquitous contaminant in aquatic ecosystems. Despite the relative sensitivity of aquatic species to pesticides, growing evidence suggests that populations can respond to pesticides by evolving higher baseline tolerance or inducing a higher tolerance via phenotypic plasticity. While both mechanisms can allow organisms to persist when faced with pesticides, resource allocation theory suggests that tolerance may be related to resource acquisition by the organism. Using Daphnia pulex, we investigated how algal resource availability influenced the baseline and inducible tolerance of D. pulex to a carbamate insecticide, carbaryl. Individuals reared in high resource environments had a higher baseline carbaryl tolerance compared to those reared in low resource environments. However, D. pulex from low resource treatments exposed to sublethal concentrations of carbaryl early in development induced increased tolerance to a lethal concentration of carbaryl later in life. Only individuals reared in the low resource environment induced carbaryl tolerance. Collectively, this highlights the importance of considering resource availability in our understanding of pesticide tolerance.

Eutrophic status influences the impact of pesticide mixtures and predation on Daphnia pulex populations

“…I, insecticide = chlorpyrifos; H, herbicide = diuron; P, predation. Raw data are provided in Table S6 growth of the surviving organisms and contribute to a larger reproductive success (Wuerthner et al, 2019). A possible explanation for the observed delayed recovery in this scenario is the accumulation of chlorpyrifos in algae (Lal et al, 1987), and the continued uptake by D. pulex after dissipation of the dissolved fraction from the water column.…”

Evaluating the fitness consequences of plasticity in tolerance to pesticides

“…However, costs of plasticity have been notoriously difficult to demonstrate (Van Buskirk & Steiner, 2009) and may be negligible in all but highly plastic genotypes (Lind & Johansson, 2009). Additionally, both costs and limits of plasticity may be diminished in environments with abundant resources (Auld et al, 2010; Moret & Schmid‐Hempel, 2000; Snell‐Rood et al, 2015; Wuerthner et al, 2019). For this reason, we reared our individuals on restricted diets, but cannot be sure that resources did not play a role in the observed absence of costs or limits.…”

Evolutionary mechanisms underpinning fitness response to multiple stressors in Daphnia

“…Biocide impact on freshwater species has been shown to be more severe in presence of predation (Jansen, Coors, et al, 2011 ), possibly explained by changes in energy storage and metabolism required in predator avoidance mechanisms (Beckerman et al, 2007 ; Oda et al, 2019 ). Resource availability can change the tolerance level to biocides; higher resource availability enables higher baseline tolerance than limiting resource availability, indicating that adaptive potential of species is not only stressor‐dependent but also influenced by the interaction among multiple stressors (Wuerthner et al, 2019 ). For example, algal resource availability and insecticides show antagonistic effects on invertebrates in microcosm experiments, impacting abundance, biomass, richness, size, structure, and composition of the community (Chara‐Serna & Richardson, 2018 ).…”

“…The number of studies on multiple stress exposure is increasing, providing us with a better understanding of the fitness costs associated with exposure to complex environments (e.g., Cuenca‐Cambronero et al, 2018 ; Cuenca‐Cambronero et al, 2018 ; Jansen, De Meester, et al, 2011 ; Wuerthner et al, 2019 ; Zhang et al, 2019 ). However, we do not know how past exposure to multiple stressors influences response mechanisms to modern environments (but see Cuenca‐Cambronero et al, 2018 ; Cuenca‐Cambronero et al, 2018 ) and how multiple stressors may influence evolutionary responses through time.…”