Prediction of suitable habitat and spread of Leptoglossus occidentalis in East Asia

The western conifer seed bug (Leptoglossus occidentalis) has recently expanded across East Asia, raising concerns regarding its potential impact on cone production and conifer-associated biodiversity. This study aimed to identify suitable habitats and evaluate invasion trajectories under realistic host constraints to support early detection and management. We developed a MaxEnt model using occurrence records and selected environmental variables, restricted predictions by conifer abundance to reflect host availability, and linked suitability to colonization probabilities. These outputs were incorporated into a cellular automaton framework that accounted for local flight dispersal and multiple levels of traffic-mediated long-distance dispersal over a 20-year period. The model identified high suitability across conifer-dominated regions of eastern China, Japan, Korea, and parts of Russia. Simulations indicated that, without long-distance dispersal, spread remained limited and fragmented, whereas even very low probabilities of human-assisted movement produced rapid, discontinuous expansion, and higher probabilities led to a much broader occupation of suitable habitats. These findings suggest that the species poses a substantial risk of establishing across major conifer regions in East Asia, emphasizing the need for proactive monitoring at transportation hubs and targeted protection of biodiversity-relevant conifer forests.