How thermal evolution may affect trophic interactions and its implications for trophic system stability remains unstudied. To advance insights in how global warming shapes trophic interactions, we need to consider besides increases in mean temperatures, also daily thermal fluctuations (DTF) and heat waves (HW), and how their effects are modulated by thermal evolution.

Using a common-garden approach we tested how each thermal factor affected predator metabolic rate and functional response parameters, and used these responses to predict long-term predator-prey interaction strength between larvae of the damselfly Ischnura elegans and the water flea Daphnia magna. By using high- and low-latitude predator populations with the latter being exposed to higher mean temperatures, higher DTF and more frequent HW, we assessed the potential impact of thermal evolution at the high latitude using a space-for-time substitution.

In line with thermal adaptation, growth rates were faster and handling times shorter in low-latitude compared to high-latitude larvae at 24°C, while the opposite was true at 20°C. Warming weakened the long-term interaction strength, except for the high-latitude trophic system at DTF and HW where plastic responses therefore may not stabilize the high-latitude system. This extends the emerging insight that temperature variation may make ectotherms more vulnerable to warming. The contributions of metabolic rate, search rate and handling time in shaping thermal effects on interaction strength often differed between latitudes. A key finding was that thermal evolution may further weaken the long-term interaction strength of the high-latitude trophic system under increases in mean temperatures, even at DTF and potentially also at HW.

Our results underscore the importance of daily thermal fluctuations and heat waves in shaping predator-prey interactions, and may suggest an overall stabilizing contribution of predator thermal evolution ameliorating thermal plastic effects on food web stability.

This dataset contains the growth rates, functional responses, metabolic rates of the damselfly I. elegans larvae from low- and high- latitudes at 20 and 24°C under different thermal variation scenarios (constant, 10°C daily temperature fluctuations, and a 32°C heat wave).

1. For datasheet "growth_rate": ID = damsefly individual IDl; F0 date = date the larva reached final larval instar; origin = damselfly origin (s = south, n = north);  population = damslefly population ID; mother = mother damsefly ID; treatment = thermal variation (cte = constand, dtv = daily temperature variation, hw = heatwave) + mean temperautre (20 = 20°C, 24 = 24°C) treatment; ori_temp = local mean summer temperature; m_dev_temp = mean developmental temperature; vtype = thermal variation type; replicate_FR = replicate ID of the functional response mesurement; initial_mass = fresh weight at day 3 at final larval instar (mg),;final_mass = fresh weight at day 8 at final larval instar (mg).
2. For datasheet "functional response": ID = damsefly individual IDl; F0 date = date the larva reached final larval instar; origin = damselfly origin (s = south, n = north);  population = damslefly population ID; mother = mother damsefly ID; treatment = thermal variation (cte = constand, dtv = daily temperature variation, hw = heatwave) + mean temperautre (20 = 20°C, 24 = 24°C) treatment; m_dev_temp = mean developmental temperature; replicate_FR = replicate ID of the functional response mesurement; final_mass = fresh weight at day 8 at final larval instar (mg); prey_num = initial D. magna density; consumed = D. magna consumed after 24 h.
3. For datasheet "metabolic rate": ID = damsefly individual IDl; origin = damselfly origin (s = south, n = north);  population = damslefly population ID; fr_type = thermal variation (cte = constand, dtv = daily temperature variation, hw = heatwave) treatment;  treatment = thermal variation (cte = constand, dtv = daily temperature variation, hw = heatwave) + mean temperautre (20 = 20°C, 24 = 24°C) treatment; replicate_MR = replicate ID of the metabolic rate mesurement. adj_d_ppm = damselfly oxeygen concentration depletion after 24 h, adjusted by control (damsefly-free) measurements; final_mass = fresh weight at day 8 at final larval instar (mg).