Keeping up with climate change: have Arctic arthropods reached their phenological limits?

Many arthropods show earlier seasonal activity with warming, but these responses cannot continue indefinitely. Identifying such phenological thresholds is crucial for understanding limits to climate tracking and species persistence, but few studies test for breakpoints that may indicate physiological or ecological constraints. Using a 28-year time series, we examined breakpoint responses to snowmelt and temperature across 15 arthropod taxa in seven plots from high-Arctic Greenland, a region experiencing pronounced warming. Our meta-analysis found breakpoint responses in two of six phenological driver and event combinations: onset and peak activity advanced with earlier snowmelt until a threshold, beyond which the relationship levelled off. A breakpoint for peak activity in response to temperature disappeared when snowmelt was included in the model, underscoring the importance of considering several environmental cues to prevent incorrect inferences about plasticity limits. Most responses showed no evidence of a breakpoint in phenological sensitivity, instead exhibiting continued tracking of cues over the study period. Our findings suggest that while many Arctic arthropods remain responsive to climate change, some may be approaching limits, potentially altering ecological interactions and vulnerability to abiotic cues. Our findings highlight the need for broader assessments of phenological thresholds to refine predictions of species responses to environmental change.