Climatic Niche Contraction and Refugial Persistence of an Invasive Tephritid Pest Across the Arabian Peninsula Under Contrasting Emission Scenarios

The peach fruit fly, Bactrocera zonata (Saunders) (Diptera: Tephritidae), is a climate-sensitive agricultural invader that threatens fruit production across the Arabian Peninsula, yet its realized climatic niche and future exposure under warming remain insufficiently resolved. We used Maximum Entropy (MaxEnt) modeling to quantify current and projected habitat suitability across the region (~3.2 million km2) under two Shared Socioeconomic Pathway scenarios (SSP1-2.6 and SSP5-8.5) for the 2050s and 2070s, based on 55 spatially filtered occurrence records and seven non-collinear environmental predictors, with sampling bias controlled using a Gaussian kernel density bias file. Model performance was robust, with mean training AUC of 0.922 ± 0.011 (SD) and mean TSS of 0.538 ± 0.115 (SD; range: 0.368–0.692), indicating moderate variability across replicates. Suitability was governed primarily by elevation, mean temperature of the driest quarter (Bio 9), mean diurnal temperature range (Bio 2), and precipitation of the coldest quarter (Bio 19), which together contributed over 97% of the model output, indicating strong climatic and topographic control on range persistence. Under present conditions, 790,714 km2, or 28.38% of the study area, was suitable, concentrated in the southwestern highlands of Saudi Arabia and Yemen, the Omani mountain ranges, and coastal fringes of the Arabian Gulf and Gulf of Oman. Future projections showed a consistent net contraction of suitable habitat across all scenarios, from 7.4% under SSP1-2.6 in the 2050s to 28.0% under SSP5-8.5 in the 2070s. In all cases, contraction exceeded expansion, although the eastern Omani highlands remained a potential climatic refugium. These patterns indicate that warming is likely to reorganize rather than uniformly expand suitability, providing a spatial basis for climate-informed biosecurity, surveillance, and regional pest management.