Small gains, large losses: range shifts of the hoverfly Dioprosopa clavata (Fabricius, 1794) (Diptera: Syrphidae) to 2100.

Climate change is rapidly reshaping species distributions and threatening ecosystem services, yet continent-wide forecasts for Neotropical hoverflies are virtually absent. Here, we present the first large-scale ecological niche modeling assessment for Dioprosopa clavata (Fabricius, 1794), a key syrphid with dual ecological roles in pollination and aphid control. Using 1,214 curated occurrences and an ensemble of MaxEnt, DOMAIN, and GLM, we combined climatic and physiographic predictors (elevation, compound topographic index, profile curvature) to project suitability under SSP2–4.5 (intermediate) and SSP5–8.5 (high-end) scenarios for 2021–2040 and 2081–2100. Models showed excellent predictive performance, with climate explaining ~ 71% of model contribution and physiography ~ 29%, highlighting the buffering role of topographic heterogeneity. Near-term projections retained most of the current range (≈ 88–89% stability), but late-century forecasts revealed dramatic contractions, up to 43.5% habitat loss under SSP5–8.5, particularly in tropical lowlands of northern South America and Central America. These losses were accompanied by increased spatial fragmentation and modest poleward and upslope gains, suggesting climate-driven range shifts toward cooler, higher-elevation refugia. Our findings indicate that D. clavata habitats will decline most severely where pollination and pest control services are most needed, agricultural regions of tropical South America, potentially reducing local ecosystem service provision. By identifying priority areas for connectivity and microclimatic refugia, this study offers a mechanical aware forecast and actionable hypotheses to guide field validation, monitoring programs, and climate-smart conservation strategies for an understudied yet functionally crucial pollinator group.