Background/Question/Methods The Formosan subterranean termite Coptotermes formosanus Shiraki (FST) was introduced into the United States from Asia following World War II and was first detected in the mid 1960’s in the Southeast. Unlike native subterranean termite species, C. formosanus commonly inhabits living trees. In addition to being a major structural pest, it causes unquantifiable aesthetic damage and poses a threat to the health of urban and rural forests. Current or previous infestations have been reported in 129 counties in eleven states and the known range continues to expand, indicating the need to minimize establishment in new areas.
We used the DOMAIN modeling method (DIVA_GIS software) to fit current range and physiological limitations to climate data. Two models were created to predict where the Formosan termite is likely to become established if introduced. A literature-based model used reported temperature tolerances from laboratory studies and climatic characteristics of the termite’s native range. The second model was constructed from the current U.S. distribution. Climate variables considered for inclusion in the model were selected based on potential biological significance to FST’s success. We used correlation and principal components analysis to select variables correlated with FST presence while eliminating redundant variables.
Results/Conclusions In addition to the currently infested states, the literature-based model predicts that parts of Nevada, Arizona, New Mexico, and Oklahoma have suitable climates for the termite’s establishment. The empirical model provides a similar estimate in the Southeast, but predicts a larger range on the west coast. Because this species can nest inside structures, populations are sometimes found where climatic conditions may prevent it from becoming widely established in the landscape. While areas surrounding these infestations require diligent monitoring, they may cause empirical models to overestimate potential range.
The potential range expansion of FST is a function of: 1) dispersal, 2) survival, and 3) reproduction. Dispersal may occur as a result of nuptial flights, colony budding, or human-mediated transport. Maximum flight distances recorded for reproductives are <900m, resulting in a slow natural rate of spread - about 1km per decade. However, FST is spread much more quickly through introductions by man. The ultimate distribution will largely depend on new introductions. These models fit the survival and reproduction aspects of FST distribution. In future studies we will identify factors that increase risk of introduction and incorporate these data into a model that will aid in conducting more focused field surveys.