Macro- and microecological responses of Arctic aphids to climate change: linking distributional shifts and microscale environmental drivers

Understanding how Arctic ectotherms persist in the face of rapid environmental change requires integrating climatic, ecological, and microscale perspectives. Here, we integrate macroclimatic projections with field-based ecological observations by combining ecological niche modelling (ENM), field surveys, and fine-scale habitat observations to assess both regional climatic suitability and local environmental constraints for three Svalbard aphid species: the High Arctic endemics Acyrthosiphon svalbardicum and Macrosiphum calvulum, and the circumpolar, subterranean Pemphigus populiglobuli. These taxa represent contrasting life strategies – above-ground, host-specific, holocyclic specialists versus a soil-dwelling, anholocyclic generalist – providing a unique lens how climate change operates across ecological scales in polar ecosystems. At the macroecological scale, ENM projections reveal contrasting responses to future warming. Acyrthosiphon svalbardicum is predicted to lose much of its suitable habitat, consistent with a climate-driven “range squeeze”, M. calvulum to retain or modestly expand, and P. populiglobuli to broaden its potential distribution. Field observations, however, show that realized occurrences are far more restricted, underscoring the role of microscale heterogeneity. Acyrthosiphon svalbardicum persists only in thermally favourable Dryas octopetala tundra, M. calvulum in nutrient-enriched Salix polaris refugia, and P. populiglobuli in insulated soils limited by near-surface temperature and moisture. Due to their close association with host–plant phenology, soil microclimate, and moisture, these aphids serve as sensitive indicators of climate-driven environmental transitions in Arctic tundra ecosystems. Under continued Arctic warming, local habitat stability and phenological synchrony may increasingly limit species persistence, underscoring the importance of incorporating microscale processes into climate-impact assessments in high-latitude systems. Comparable interactions between regional climate forcing and fine-scale environmental heterogeneity are likely to govern invertebrate persistence across other Arctic and alpine regions, where strong climatic gradients operate over short spatial scales.