TY  - JOUR
A1  - Koussoroplis, Apostolos-Manuel
A1  - Schälicke, Svenja
A1  - Raatz, Michael
A1  - Bach, Moritz
A1  - Wacker, Alexander
T1  - Feeding in the frequency domain
BT  - Coarser-grained environments increase consumer sensitivity to resource variability, covariance and phase
JF  - Ecology letters
N2  - Theory predicts that resource variability hinders consumer performance. How this effect depends on the temporal structure of resource fluctuations encountered by individuals remains poorly understood. Combining modelling and growth experiments with Daphnia magna, we decompose the complexity of resource fluctuations and test the effect of resource variance, supply peak timing (i.e. phase) and co-limiting resource covariance along a gradient from high to low frequencies reflecting fine- to coarse-grained environments. Our results show that resource storage can buffer growth at high frequencies, but yields a sensitivity of growth to resource peak timing at lower ones. When two resources covary, negative covariance causes stronger growth depression at low frequencies. However, negative covariance might be beneficial at intermediate frequencies, an effect that can be explained by digestive acclimation. Our study provides a mechanistic basis for understanding how alterations of the environmental grain size affect consumers experiencing variable nutritional quality in nature.
KW  - Cholesterol
KW  - covariance
KW  - Daphnia
KW  - digestive acclimation
KW  - dynamic energy budgets
KW  - food quality
KW  - phosphorus
KW  - storage
KW  - unbalanced diets
Y1  - 2019
U6  - https://doi.org/10.1111/ele.13267
SN  - 1461-023X
SN  - 1461-0248
VL  - 22
IS  - 7
SP  - 1104
EP  - 1114
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Koussoroplis, Apostolos-Manuel
A1  - Wacker, Alexander
T1  - Covariance modulates the effect of joint temperature and food variance
on ectotherm life-history traits
JF  - Ecology letters
N2  - Understanding animal performance in heterogeneous or variable environments is a central question in ecology. We combine modelling and experiments to test how temperature and food availability variance jointly affect life-history traits of ectotherms. The model predicts that as mean temperatures move away from the ectotherm's thermal optimum, the effect size of joint thermal and food variance should become increasingly sensitive to their covariance. Below the thermal optimum, performance should be positively correlated with food–temperature covariance and the opposite is predicted above it. At lower temperatures, covariance should determine whether food and temperature variance increases or decreases performance compared to constant conditions. Somewhat stronger than predicted, the covariance effect below the thermal optimum was confirmed experimentally on an aquatic ectotherm (Daphnia magna) exposed to diurnal food and temperature variance with different amounts of covariance. Our findings have important implications for understanding ectotherm responses to climate-driven alterations of thermal mean and variance.
KW  - Biotic interactions
KW  - co-limitation
KW  - Daphnia
KW  - environmental fluctuations
KW  - heterogeneity
KW  - variability
KW  - vertical migration
KW  - zooplankton
Y1  - 2016
U6  - https://doi.org/10.1111/ele.12546
SN  - 1461-023X
SN  - 1461-0248
VL  - 19
SP  - 143
EP  - 152
PB  - Wiley-Blackwell
CY  - Hoboken
ER  -