Risk Assessment of the Worldwide Expansion and Outbreak of Massicus raddei (Blessig) (Coleoptera: Cerambycidae) Based on Host Plant and Climatic Factors

SIMPLE SUMMARY: The oak longhorned beetle (OLB), Massicus raddei (Blessig, 1872) is a well-known wood borer of oak species throughout eastern Asia, recently pest outbreaks have occurred in northeastern regions of China. Therefore, the knowledge about the global potential distribution of this borer is necessary to develop prompt monitoring or control strategies in its distribution-free areas. Here, we highlighted the global habitat suitability of OLB with host distribution and climatic factors using the Maxent model to present the worldwide potential distribution of this borer. To our best knowledge, this is the first modelling study of this trunk borer. Our results shed light on major ecological factors that shape its spatial suitability pattern, selected high risky areas threatened by this borer, provided fundamental information to take precise quarantine measures to prevent further invasion and outbreaks of this borer at the global scale. ABSTRACT: Massicus raddei (Blessig) is a serious trunk borer of oak species, currently widespread only in eastern Asia. A better understanding of the invasive potential of this borer across other distribution-free areas is further needed to prevent its invasion and outbreaks. In this study, we mapped the current distribution of M. raddei, two susceptible hosts (Quercus mongolia and Q. liaotungensis) and all 11 host species of this borer, and then modeled their potential distributions. We comprehensively compared the current distributions and potential invasion ranges among M. raddei, susceptible hosts and all hosts to select areas at risk for the establishment of this borer. MaxEnt model predictions revealed that (1) the central and eastern US, a small area of central and western Europe, western Georgia, and central Argentina had suitable climates for M. raddei. Such highly suitable areas for this borer overlapped considerably with the current plantation and potential distributions of its hosts. Consequently, susceptible hosts and climate suitability together create the highest risk for M. raddei establishment and outbreaks, throughout central and eastern America, a small area of central Europe, western Norway and western Georgia, and (2) the broad host suitability across six continents creates a situation favorable for the colonization of this borer, further extending the spatial scale of possible infestation by M. raddei worldwide.