# Quantifying Key Environmental Determinants Shaping the Ecological Niche of Fruit Moth Carposina sasakii Matsumura, 1900 (Lepidoptera, Carposinidae)

## TL;DR

This study identifies key climate factors influencing the spread of a fruit tree pest, Carposina sasakii, and predicts how climate change will shift its habitat.

## Contribution

The study introduces a new migration model and quantifies the role of July precipitation as a dispersal threshold for the pest under climate change.

## Key findings

- July precipitation is the most critical determinant of C. sasakii distribution, with a threshold of approximately 370 mm.
- Future climate scenarios suggest a 'coastal contraction–inland transfer' migration pattern for the pest.
- The pest's suitable habitat is projected to expand under moderate emission scenarios but shrink under high-emission pathways.

## Abstract

This study investigates a significant fruit tree pest, Carposina sasakii, under global climate change. We quantified nonlinear responses of its distribution to precipitation, identifying July precipitation as a critical dispersal threshold. A “coastal contraction–inland transfer” migration model was developed, revealing synergistic effects of extreme temperature and precipitation on niche differentiation. The cross-border risk warning framework integrates stable East Asian sources with emerging Euro-American habitats to guide monitoring and management strategies.

Carposina sasakii Matsumura is a significant lepidopteran pest in the Carposinidae family, inflicting substantial damage on stone and pome fruit trees such as jujube, peach, and apple. Using MaxEnt, we assessed the worldwide climatic suitability for C. sasakii and its key environmental drivers, evaluating how climate change impacts dispersal risks. Integrating global occurrence records with 37 environmental variables, the model (AUC = 0.982) quantitatively identifies July precipitation (prec7), minimum average temperatures in April and August (tmin4 and tmin8, respectively), and maximum average temperature in May (tmax5) as critical distribution determinants. Among these, prec7 exhibits the highest contribution (threshold approximately 370 mm). The current suitable habitat spans 10.39 × 102 km2, concentrated predominantly in East Asia’s temperate monsoon zone (eastern China, the Korean Peninsula, and Japan) and southern North America. Under future climate scenarios, the high-emission pathway (SSP585) will reduce highly suitable areas, while moderately suitable zones expand coastward. In contrast, SSP370 projects a significant, albeit phased, habitat increase with a 19.61% growth rate. Precipitation regimes and extreme temperatures jointly regulate niche differentiation in C. sasakii, whose range shifts toward Southeast Asia and suboptimal regions in Europe and America, underscoring cascading climate change effects. These findings provide a scientific basis for transnational monitoring, early warning systems, and regional ecological governance.