Seasonal dominance of exotic ambrosia beetles compared to native species within deciduous and coniferous woodlots

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are among the most successful invaders of trees on a global scale. Exotic species can establish large populations within forested habitats and disperse into tree nurseries and orchards with the potential for substantial economic losses. Our objective was to assess the seasonal dominance of exotic Scolytinae compared to native species by characterizing their flight phenology, abundance and species diversity. Weekly sampling using ethanol-baited traps was conducted within deciduous and coniferous woodlots in Ohio, USA from March/April to September/October in 2014, 2015, 2016, and 2019. Over the course of the study, 16 native and 11 exotic species of Scolytinae were identified. No difference was detected in the number of exotic Scolytinae species or their abundance, Shannon’s index (H), and evenness (Eh) between the coniferous vs. deciduous woodlots. On average, initial flight occurred at 188 degree days (DD) for exotic species compared to 273 DD for native species. Seasonal flight duration of exotic species averaged 49 days compared to 10 days for native species. Of the 145,882 total Scolytinae captured over the four years, only 622 were native beetles. Captures of exotic Scolytinae were 341-times greater than native species across the four trapping seasons, including captures of the exotic ambrosia beetle Xylosandrus germanus being 450-times greater than the most common native species Xyloborinus politus. These results provide insight into the invasion success of ambrosia beetles and will aid in predicting and monitoring key species.