Cold tolerance and invasive potential of the redbay ambrosiabeetle (Xyleborus glabratus) in the eastern United States
Formby,J. P., Rodgers, J. C., Koch, F. H., Krishnan, N., Duerr, D. A., & Riggins,J. J. (2017). Cold tolerance and invasive potential of the redbay ambrosiabeetle (Xyleborus glabratus) in the eastern United States. Biological Invasions, 1-13. PDF.
Summary
Laurel wilt disease is caused by a fungal pathogen Raffaelea lauricola that is carried and cultivated by its symbiotic vector, the redbay ambrosia beetle (Xyleborus glabratus). Currently this invasive insect-pathogen disease complex, which is native to forests of southern Asia, is killing North American species in the Lauraceae family (e.g. sassafras, redbay) in nine southeastern US states. Laurel wilt disease can cause tree mortality in as little as 4 weeks and may ultimately cause functional extinction of redbay (Persea borbonia) and swampbay (Persea palustris) as well as lead to the crash of the Florida avocado industry. A recent jump to infest sassfras trees (Sassafras albidum) is of great concern as this native species has a distribution as far north as Canada. This may open up a pathway for this devastating invasive pathogen to move into northern forests of the US and Canada. Currently insecticides and fungicides have proven ineffective in controlling R. lauricola-X. glabratus and the major factor thought to be limiting northward expansion is cold temperatures. In this paper, Formby et al. attempt to understand the cold limitations of X. glabratys and model its potential spread via sassafras trees into northern forests under modest climate change scenarios.
Take home points
Based on a modest climate change scenario (+1.4ºC) by 2050, 91% of the area in which sassafras inhabits in the eastern US will not experience temperatures cold enough to cause any mortality in the redbay ambrosia beetle.
X. glabratus is a chill susceptible species and beetles that were more acclimated to summer temperatures were even more susceptible to cold exposure. However its reproductive biology allows for populations to recover quickly even after a greater than 50% population loss during a cold snap and therefore 100% mortality would be necessary to stop its spread.
The thermal buffered microclimate experienced by the beetles inside the trees provides protection from extreme weather events and increases the survivability of the beetle in conditions it may not otherwise be able to withstand.
Management implications
We can expect Laurel wilt disease to move north as temperatures increase with climate change. Monitoring programs at the northern edge of its current range will be important to understand its range expansion and prepare for its impacts.
Additional investments should be made to develop management strategies for this invasive species complex to prevent further range expansion.
Keywords
Range Expansion; Model; Invasive Invertebrate; Terrestrial Habitat; Xyleborus glabratus; Redbay Ambrosia Beetle; Risk Assessment