Nermeen R. Amer‡§, Maria J Golab|, Robby Stoks Stoks¶, Guillaume Wos#, Szymon Śniegula‡Corresponding author: Szymon Śniegula ( szymon.sniegula@gmail.com ) © Nermeen R. Amer, Maria J Golab, Robby Stoks, Guillaume Wos, Szymon Śniegula. This is an open access preprint distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Citation:
Amer NR, Golab MJ, Stoks R, Wos G, Śniegula S (2026) Warming and photoperiod differentially mediate native and invasive alien predator effects on damselfly fitness traits. ARPHA Preprints. https://doi.org/10.3897/arphapreprints.e201981 |  |
Invasive alien (IA) predators can disrupt predator-prey interactions and alter prey phenotypes, yet how their effects differ from those of native predators and to what extent this depends on environmental factors such as warming and seasonal time constraints remain poorly understood. To address these gaps, we performed two complementary experiments testing the effects of predator chemical cues (control, native noble crayfish, and IA spinycheek crayfish) in combination with (Experiment 1) temperature (ambient vs. warming) and exposure duration to predator cues (acute vs. chronic), or (Experiment 2) seasonal time constraints manipulated by photoperiod (early vs. late season). In both experiments, we quantified effects on life history (survival and growth rate), physiological (investments in immune function measured as phenoloxidase (PO) activity and in energy storage measured as fat content), and behavioural (boldness and feeding rate) traits in the damselfly Ischnura elegans.
In Experiment 1, responses to IA spinycheek crayfish cues often differed from those induced by native noble crayfish cues across behavioural, physiological, and life-history traits, and these differences depended strongly on temperature, sex, and exposure duration. Under ambient temperature, IA spinycheek crayfish cues reduced boldness and increased PO activity more strongly than native predator cues, whereas under warming IA predator cues increased boldness. In contrast, chronic exposure to native noble crayfish cues produced the strongest reduction in female growth rate under warming.
In Experiment 2, behavioural differences between native and IA predator cues were more pronounced under early photoperiod but weakened under late photoperiod, suggesting that strong seasonal time constraints constrained predator-specific antipredator responses. Together, our results broadly support the naïve prey hypothesis, while demonstrating that abiotic conditions and exposure duration strongly shape how prey respond to native and IA predators. These findings highlight the importance of considering interactions between predator novelty and environmental context when predicting invasion impacts under climate change.