Warming erodes individual-level variability in life history responses to predation risk in larvae of the mayflyCloeon dipterum

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Year of publication 2020
Type Article in Periodical
Magazine / Source Freshwater Biology
MU Faculty or unit

Faculty of Science

Web https://doi.org/10.1111/fwb.13619
Doi http://dx.doi.org/10.1111/fwb.13619
Keywords climate change; cohort splitting; development; growth rate; metabolic scope
Description Warming and predation risk are ubiquitous environmental factors that can modify life histories and population dynamics of aquatic ectotherms. While separate responses to each of these factors are well understood, their joint effects on individual life histories and population dynamics remain largely unexplored. Current theory predicts that the magnitude of prey behavioural, physiological, and life history responses to predation risk should diminish with warming due to the reduced metabolic scope. However, empirical support for this prediction remains equivocal, and experiments covering a substantial proportion of individual prey ontogeny until maturation are lacking. To fill these gaps, we ran a laboratory experiment to investigate how warming and non-consumptive predation risk influence life history responses in the larvae of the mayflyCloeon dipterum, an aquatic insect with highly plastic development. We reared larvae of varying initial sizes at three temperatures (21, 24, and 27 degrees C) in a risk-free environment and under predation risk signalled by chemical cues from dragonfly larvae (Aeshna cyanea), and followed their individual survival, growth, and development until emergence. SomeC. dipterumlarvae substantially prolonged their development and the proportion of theseslowindividuals declined rapidly with temperature and increased with predation risk. We attribute this response to cohort splitting, a common life history strategy of aquatic insects and other taxa in unpredictable environment. Growth, development, and maturation varied predictably with temperature in thefastlarvae that did not prolong their development. They grew and developed faster but matured at smaller sizes with increasing temperature. Predation risk tended to slow down individual growth and development in line with the reduced metabolic scope hypothesis, but the differences were relatively minor and observable only at 21 degrees C. Survival to subimago increased with predation risk, possibly due to indirect effects mediated by dissolved micronutrients, but did not vary significantly with temperature. Survival also tended to be higher in theslowindividuals. This partly compensated for a smaller final size relative to thefastindividuals and made both strategies comparable in overall fitness. Our results show that warming may erode individual-level variability in life history responses to predation risk. This implies that warming can synchronise population dynamics and consequently make such populations more vulnerable to unpredictable disturbances.
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