Global Habitat Suitability Modeling for an Invasive Species: Japanese Beetle (Popillia japonica)
Study Overview
Evaluated current and projected global habitat suitability for the invasive Japanese Beetle (Popillia japonica) using Maximum Entropy (MaxEnt) species distribution modeling. By integrating crowdsourced occurrence data from iNaturalist with key bioclimatic variables, the study compared native-to-invasive model transferability against a global random-split validation strategy. Under current climate conditions, high suitability was identified in the Eastern USA and Northern Italy (Milan/Lombardy region). Under the RCP 4.5 greenhouse gas trajectory, projections indicate a major range expansion into Central USA and Canada, alongside a dramatic shift in Europe where the species is projected to move out of Italy toward Northern Europe.
Skills & Key Highlights
- MaxEnt Modeling & Strategy Validation: Implemented Maximum Entropy species distribution modeling in MaxEnt, comparing a native-trained model (AUC = 0.468) against a global 80/20 train/test split model (AUC = 0.71) to demonstrate the necessity of pooled occurrence data for invasive species predictions.
- Eco-Physiological Risk Mapping: Analyzed bioclimatic variable response curves against known physiological thresholds of P. japonica, including thermal activity limits (21°C to 35°C), relative humidity constraints (60%), and moisture requirements for larval development.
- Climate Scenario Forecasting: Projected spatial distribution shifts under the RCP 4.5 emission scenario, forecasting that changing temperature seasonality will push the species out of its current Italian hotspot and drive expansion into higher latitudes across Europe and North America.
- Biodiversity Data Integration: Extracted, filtered, and processed global occurrence records from iNaturalist to establish training and testing datasets across native and invasive ranges.