Biological Invasions

, Volume 20, Issue 2, pp 365–374 | Cite as

Increases in summer temperatures decrease the survival of an invasive forest insect

  • Angela M. MechEmail author
  • Patrick C. Tobin
  • Robert O. Teskey
  • J. Rusty Rhea
  • Kamal J. K. Gandhi
Original Paper


Higher temperatures projected under current climate change models are generally predicted to exert an overall positive effect on the success of invasive insects through increased survivability, developmental rates and fecundity, and by facilitating geographic range expansion. However, these effects have primarily focused on the shifts in winter temperatures with limited attention to the role that summer heat may play in shaping species ranges or fitness. We examined the thermal ecology of an ecologically important invasive forest insect, the hemlock woolly adelgid (Adelges tsugae), by determining survival during its summer dormancy phase under increasing temperature regimens. From laboratory and field experiments, we documented a positive association between increased temperatures and duration of exposure, and A. tsugae mortality. Adelges tsugae mortality was minimal (<20%) when exposed to summer temperatures characteristic to its native range (<25 °C), but markedly increased (up to 100%) when exposed to temperatures that occur occasionally or rarely in natural settings (>30 °C). At the warmest, southernmost edge of their range, field mortality of A. tsugae ranged from 8.5 to 81.9% and was strongly correlated with site temperature regimens. Further, we found no significant differences in A. tsugae survival between populations collected from Maine and Georgia, and over a 3-year period within Georgia, indicating that A. tsugae may not be acclimating to heat. These results highlight the importance of including summer temperatures in studies regarding increased temperatures on insect dynamics, and may alter historical predictions of climate change impacts on invasive insects and the conservation of forest ecosystems.


Adelges tsugae Aestivation Climate change Heat stress 



We thank Jackson Audley, Brittany Barnes, Courtney Brissey, Cera Jones, Mary Ann McGuire, Lee Ogden, Derek Robertson, Ashley Schulz, and Kristopher Smoot (University of Georgia) for their support and assistance, and Ryan Hanavan (USDA Forest Service) for the Maine collections. We also thank Dr. Jaxk Reeves, Yuanwen Wang, Soyeon Jung, and Na Hao for statistical assistance (Statistical Consulting Center, University of Georgia). Financial support was provided by the USDA Forest Service Forest Health Protection, the Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, and the School of Environmental and Forest Sciences, University of Washington.

Supplementary material

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Supplementary material 1 (DOCX 342 kb)


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Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  1. 1.Daniel B. Warnell School of Forestry and Natural ResourcesUniversity of GeorgiaAthensUSA
  2. 2.School of Environmental and Forest SciencesUniversity of WashingtonSeattleUSA
  3. 3.USDA Forest Service, Forest Health ProtectionAshevilleUSA
  4. 4.School of Environmental and Forest SciencesUniversity of WashingtonSeattleUSA

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