Responses to seasonal time constraints under global change across life stages: facilitated by warming but counteracted by invasive alien predators

Abstract In seasonal environments, organisms with complex life cycles not only contend with seasonal time constraints (TC) but also increasingly face global change stressors that may interfere with responses to TC. Here, we tested how warming and predator stress imposed during the egg and larval stages shaped life history and behavioural responses to TC in the temperate damselfly Ischnura elegans. Eggs from early and late (TC) clutches in the season were subjected to current and 4°C warming temperature and the presence or absence of predator cues from native perch and invasive alien signal crayfish (IAP). After hatching, larvae were retained at the same thermal regime, and the predator treatment was continued or not up to emergence. The TC decreased egg development time, especially under warming and when not exposed to predator cues. However, the TC increased egg development time when exposed to predator cues, especially IAP cues. The TC decreased survival of larvae that were as eggs exposed to IAP cues, indicating a carry-over effect from the IAP. The TC and warming additively reduced larval development time to emergence. Independent of the TC, predator cue effects on development time were stronger during the egg than during the larval stage. The TC caused a lower mass at emergence, which mirrored the size difference between field-collected mothers. Warming caused a higher mass at emergence. The TC caused increased boldness and a higher number of moves, whereas warming caused a decreased boldness. There was no predator cue effect on larval behaviour. The results indicate that TC individuals compensate for late season egg laying, which is facilitated under warming but counteracted under predation risk, especially when imposed by the IAP.