From establishment to dominance: spatio-temporal infestation patterns of the Asian subterranean termite, Coptotermes gestroi, in Key West, Florida, 1999–2021

Abstract

The Asian subterranean termite (AST), Coptotermes gestroi (Wasmann), is a major structural pest in the world’s humid tropics. After its 1999 discovery in Key West, Florida, a survey of buildings infested with AST was initiated. By 2021, a total of 1,703 terrestrial AST encounters were accumulated and used to assess the spatio-temporal spread of AST throughout Key West and adjacent Stock Island between 2005 (which consolidates sightings between 1999 and 2005) and 2021. A lattice-based simulation model was run using selected ecological parameters to predict the infestation locations of AST on Key West from initial encounter points. The distances between annual AST encounters and the nearest marine dockage were compared with the distances between random locations in built areas and the nearest marine dockage. Results show that for the majority of the first ten years up to 2014, the median distance between AST encounters and nearest dockage was significantly smaller than between random points and nearest dockage, but after 2016 encounters became significantly larger for most years. This supports the hypothesis that AST infestations originated from marine dockage (i.e., infested boats). The gradual spread to inland infestations on the island was reflected by a shift of the annual centroid locations westward where domicile density is the greatest. The simulation underestimated the actual extent of infestation in 2021, suggesting secondary non-marine infestation foci. It was concluded that infested trees, for which no records were available, were probably the secondary source of AST spread, and that cryptic tree infestations may have facilitated this accelerated spread. The gradual growth and spread of infested areas were reflected in an increased radius of gyration for annual infested point locations, which also indicated that the AST sites reached saturation and stabilized during the last few years of analysis.