Future Extreme Climatic Events May Reshape Butterfly Distributions Across Biomes in Italy

Aim Extreme climatic events (ECEs) are increasingly recognized as major drivers of insect declines, yet remain rarely incorporated into biodiversity projections. Butterflies may be especially sensitive to prolonged ECEs because they are short‐lived ectotherms, while voltinism can influence their capacity to absorb climatic shocks. We assessed how the frequency of prolonged ECEs may reshape butterfly climatic suitability and richness patterns across Italy and whether responses vary among biomes and voltinism classes. Location Italy. Time Period Baseline (1971–2000) and mid‐century (2041–2070). Major Taxa Studied Diurnal butterflies (Papilionoidea). Methods We derived spatially explicit indices of hot, cold, dry and wet spells from EURO‐CORDEX climate projections and used them to build ensemble species distribution models for 199 butterfly species. We mitigated sampling bias with a target‐group pseudo‐absence approach and defined ecologically meaningful calibration areas based on occupied biomes. We projected changes in climatic suitability and richness under Representative Concentration Pathway (RCP) 2.6, a mitigation scenario, and RCP8.5, a high‐emission scenario, and compared responses among biomes and voltinism classes. Results Projected suitability changes were predominantly negative across all biomes and consistently stronger under RCP8.5 than under RCP2.6. Univoltine species were most negatively affected, whereas bivoltine and multivoltine species showed broader and more heterogeneous responses. Mediterranean and Temperate Broadleaf assemblages showed marked suitability declines and widespread richness losses under RCP8.5. Temperate Conifer assemblages showed smaller percentage suitability declines but greater richness losses, suggesting that even moderate suitability reductions may translate into strong impacts in montane ecosystems. These patterns also reflected biome‐specific changes in ECE frequencies, although scenarios generally indicated more frequent hot spells and fewer cold spells across biomes. Main Conclusions Future ECEs may substantially reshuffle butterfly assemblages across Italy, with impacts varying among biomes and voltinism classes. Explicitly integrating spell‐based ECE indices into biodiversity projections may improve assessments of climate‐change impacts on insects and inform proactive conservation planning.