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Global climate change is expected to both increase average temperatures as well as temperature variability. Increased average temperatures have led to earlier breeding in many spring‐breeding organisms. However, individuals breeding earlier will also face increased temperature fluctuations, including exposure to potentially harmful cold‐temperature regimes during early developmental stages. Using a model spring‐breeding amphibian, we investigated how embryonic exposure to different cold‐temperature regimes (control, cold‐pulse, and cold‐press) affected (a) compensatory larval development and growth, (b) larval susceptibility to a common contaminant, and (c) larval susceptibility to parasites. We found: (a) no evidence of compensatory development or growth, (b) larvae exposed to the cold‐press treatment were more susceptible to NaCl at 4‐days post‐hatching but recovered by 17‐days post‐hatching, and (c) larvae exposed to both cold treatments were less susceptible to parasites. These results demonstrate that variation in cold‐temperature regimes can lead to unique direct and indirect effects on larval growth, development, and response to stressors. This underscores the importance of considering cold‐temperature variability and not just increased average temperatures when examining the impacts of climate disruption.

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.

Human activities are rapidly changing natural environments, often with harmful consequences for native communities. The introduction of invasive species is particularly damaging to native communities, especially when invasive species alter the chemical environment and create novel, stressful conditions. These abiotic conditions are predicted to favor other stress-tolerant organisms, potentially shifting community abundance and diversity over time. However, few environments are free of other anthropogenic stressors (i.e., chemical contaminants), which can also influence patterns of abundance and diversity. Therefore, to understand the impacts of invasive species, we need to consider their potential interactions with other anthropogenic stressors. Towards this goal, we tested how leachates from invasive plants and road salt impacted a model amphibian that is native to the U.S. (northern leopard frog, Lithobates pipiens) and a model amphibian that is non-native to the U.S. and considered invasive in some localities (African clawed frog, Xenopus laevis). We examined the effects of native and invasive leaf litter leachate and sublethal NaCl concentrations on amphibian development, size, and tolerance to a lethal concentration of NaCl. Exposure to invasive leaf litter and sublethal NaCl both accelerated hatching time in leopard frogs, but neither affected hatching time in Xenopus. Exposure to invasive leaf litter also led to reduced mass and tolerance to lethal NaCl concentrations in the leopard frog, but had no effect on mass and led to increased tolerance to lethal NaCl concentrations in Xenopus. These findings suggest that invasive leaf litter leachate impacts these amphibian species differently, being more stressful to the leopard frog than Xenopus. Further, we demonstrate that the presence of a pollutant may augment the effect of invasive leaf litter on amphibians, highlighting the need to consider concurrent stressors in invasive species management.

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.