Linking trophic interactions to plasticity in thermal sensitivity of geographically separated populations of a herbivore

Rosenblatt, Adam; Crowley, Bryan T.; Schmitz, Oswald J.

doi:10.1007/s10682-016-9827-6

Cited by 17 publications

(22 citation statements)

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“…The low temperature (15°C) was chosen because it represents the lower end of thermal conditions M. femurubrum grasshopper populations could experience for prolonged periods during the summer growing season in the field (Rosenblatt et al. ). The middle temperature (25°C) approximates average summer growing temperatures that field populations could experience (Rosenblatt et al.…”

Section: Methodsmentioning

confidence: 99%

“…The middle temperature (25°C) approximates average summer growing temperatures that field populations could experience (Rosenblatt et al. ). The high temperature (35°C) represents upper extreme levels that field populations could experience (Rosenblatt et al.…”

Section: Methodsmentioning

confidence: 99%

“…The terraria were transferred to one of three environmental control chambers (Percival Scientific, Inc., Perry, Iowa, USA) set at either 15°C, 25°C, or 35°C with a constant relative humidity of 40% and light levels that matched the day-night cycle of ambient field conditions. The low temperature (15°C) was chosen because it represents the lower end of thermal conditions M. femurubrum grasshopper populations could experience for prolonged periods during the summer growing season in the field (Rosenblatt et al 2016). The middle temperature (25°C) approximates average summer growing temperatures that field populations could experience (Rosenblatt et al 2016).…”

Section: Experimental Designmentioning

confidence: 99%

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Temperature dependence of predation stress and the nutritional ecology of a generalist herbivore

Schmitz

Rosenblatt

Smylie

2016

Ecology

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Abstract. Prey at risk of predation may experience stress and respond physiologically by altering their metabolic rates. Theory predicts that such physiological changes should alter prey nutrient demands from N-rich to C-rich macronutrients and shift the balance between maintenance and growth/reproduction. Theory further suggests that for ectotherms, temperature stands to exacerbate this stress. Yet, the interactive effects of predation stress and temperature stress on diet, metabolism, and survival of ectotherms are not well known. This knowledge gap was addressed with a laboratory study in which wild juvenile grasshoppers were collected, assigned to one of three groups, and raised at three different temperatures. All grasshoppers had access to equal quantities of two diets composed of opposite carbohydrate : protein ratios. Half of the individuals in each temperature group were exposed to predation risk cues from spider predators, while the other half were kept in risk free conditions. Grasshoppers consumed more carbohydrates when exposed to predation risk, but consumption favored greater protein intake as temperature increased. Moreover, the difference in carbohydrate intake between risk cue and risk free treatments diminished as temperature increased. Furthermore, variability between individual consumption patterns both within and between treatments decreased markedly as temperature increased, suggesting that higher temperatures promote more consistent individual consumption behaviors. Grasshoppers grew faster and larger as temperature increased, which translated into higher survival rates at higher temperatures. Warmer grasshoppers also did not alter their metabolic rates in response to predation risk cues, in contrast to colder grasshoppers. Digestive efficiency increased with temperature as well --further indicating that lower temperatures were much more stressful than higher temperatures for grasshoppers. The study shows that physiological responses of ectothermic herbivores to predation stress are highly plastic and temperature dependent, with higher temperatures promoting increased protein intake, growth, development, survival, and digestive efficiency relative to colder temperatures. These findings help to reconcile why dietary responses (proportion of protein vs. carbohydrate intake) to predation stress may vary among different prey taxa studied previously.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Experimental Designmentioning

confidence: 99%

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Temperature dependence of predation stress and the nutritional ecology of a generalist herbivore

Schmitz

Rosenblatt

Smylie

2016

Ecology

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“…These targets may also change as a function of environmental conditions (Rosenblatt et al. , Schmitz et al. ), so it is not surprising that grasshoppers shift their diet in the presence of predators.…”

Section: Discussionmentioning

confidence: 99%

“…While other factors including temperature may elevate metabolism and alter diet (Rosenblatt et al. , Schmitz et al. ), most studies have found that dietary preferences of grasshoppers are invariant across temperatures and driven entirely by predation risk (Barton and Schmitz , Barton et al.…”

Section: Introductionmentioning

confidence: 99%

Covariance between predation risk and nutritional preferences confounds interpretations of giving‐up density experiments

McMahon

Lashley

Brooks

et al. 2018

Ecology

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Giving-up density (GUD) experiments have been a foundational method to evaluate perceived predation risk, but rely on the assumption that food preferences are absolute, so that areas with higher GUDs can be interpreted as having higher risk. However, nutritional preferences are context dependent and can change with risk. We used spiders and grasshoppers to test the hypothesis that covariance in nutritional preferences and risk may confound the interpretation of GUD experiments. We presented grasshoppers with carbohydrate-rich and protein-rich diets, in the presence and absence of spider predators. Predators reduced grasshopper preference for the protein-rich food, but increased their preference for the carbohydrate-rich food. We then measured GUDs with both food types under different levels of risk (spider density, 0-5). As expected, GUDs increased with spider density indicating increasing risk, but only when using protein-rich food. With carbohydrate-rich food, GUD was independent of predation risk. Our results demonstrate that predation risk and nutritional preferences covary and can confound interpretation of GUD experiments.

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Altered spring phenology of North American freshwater turtles and the importance of representative populations

Janzen

Hoekstra

Brooks

et al. 2018

Ecology and Evolution

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Globally, populations of diverse taxa have altered phenology in response to climate change. However, most research has focused on a single population of a given taxon, which may be unrepresentative for comparative analyses, and few long‐term studies of phenology in ectothermic amniotes have been published. We test for climate‐altered phenology using long‐term studies (10–36 years) of nesting behavior in 14 populations representing six genera of freshwater turtles (Chelydra, Chrysemys, Kinosternon, Malaclemys, Sternotherus, and Trachemys). Nesting season initiation occurs earlier in more recent years, with 11 of the populations advancing phenology. The onset of nesting for nearly all populations correlated well with temperatures during the month preceding nesting. Still, certain populations of some species have not advanced phenology as might be expected from global patterns of climate change. This collection of findings suggests a proximate link between local climate and reproduction that is potentially caused by variation in spring emergence from hibernation, ability to process food, and thermoregulatory opportunities prior to nesting. However, even though all species had populations with at least some evidence of phenological advancement, geographic variation in phenology within and among turtle species underscores the critical importance of representative data for accurate comprehensive assessments of the biotic impacts of climate change.

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Linking trophic interactions to plasticity in thermal sensitivity of geographically separated populations of a herbivore

Cited by 17 publications

References 50 publications

Temperature dependence of predation stress and the nutritional ecology of a generalist herbivore

Temperature dependence of predation stress and the nutritional ecology of a generalist herbivore

Covariance between predation risk and nutritional preferences confounds interpretations of giving‐up density experiments

Altered spring phenology of North American freshwater turtles and the importance of representative populations

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