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A DNA-BARCODING APPROACH TO THE IDENTIFICATION OF INVASIVE AMBROSIA BEETLES IN LUMPKIN COUNTY, GEORGIA

Abstract

Ambrosia beetles (Curculionidae: Scolytinae and Platypodinae) are native and non-native pests of dead, unhealthy, and/or even healthy trees which can have major commercial impact. Boring galleries in which they grow fungi to feed their larvae, beetles injure or kill host trees and devalue wood. Although native ambrosia beetles exist in Georgia, an increase in global trade has introduced at least 19 exotic species into the state. In the spring of recent years, SAW has noted large enough numbers of ambrosia beetles locally in Lumpkin County, Georgia, to suggest invasive activity. In some cases beetle numbers were sufficient to force people indoors. To determine if these beetles were exotic, collections were made, and identifications were established using a DNA barcoding approach. About two-hundred beetles belonging to five morphotypes were collected March-July 2021. DNA was extracted from crushed whole beetles from one or more representatives of each type. We amplified and sequenced 712 nucleotides of mitochondrial cytochrome c oxidase subunit I following standard molecular methods. Sequences were proofread by hand from both strands, and compared against publicly-available sequences using standard bioinformatics approaches. Homology assessment using percent identity (100% match criterion) resulted in the identification of four known exotic ambrosia beetles (numbers sequenced given): Xylosandrus crassiusculus (6), Euwallacea interjectus (3), Cnestus mutilatus (1), and Xyleborinus saxesenii (1). All four of these non-native species have been previously collected in Georgia, however C. mutilatus might represent a range extension. No native ambrosia beetles have been identified from our collections. Additionally, one sequenced individual was identified as a weevil of the Molytinae (non-ambrosia beetle curculionid). While we did not discover any exotic taxa new to the state of Georgia, further research regarding the spread of invasive ambrosia beetles, especially in regions with lumber and fruit trees at high density, could be useful for the protection of trees and the state economy.

Acknowledgements

Funding was provided by the John and Mary Franklin Foundation and a USG STEM IV grant to Dean John Leyba (UNG College of Science & Mathematics). The UNG Department of Biology also provided support. K. Fadroski and M. Davis reviewed earlier versions of this abstract.

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