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Effects of Elevated CO2 on Longevity and Fecundity of an Invasive Weevil Feeding on Aspen, Birch and Maple Foliage
Hillstrom, M.L., Vigue, L.M., Coyle, D.R., Raffa, K.F. and Lindroth, R.L. 2010. Performance of the invasive weevil Polydrusus sericeus is influenced by atmospheric CO2 and host species. Agricultural and Forest Entomology 12: 285-292.

The authors write that "natural forest systems constitute a major portion of the world's land area, and are subject to the potentially negative effects of both global climate change and invasion by exotic insects," and they report, in this regard, that "a suite of invasive weevils has become established in the northern hardwood forests of North America," while noting that how these insects will respond to continued increases in the air's CO2 content is "unknown."

What was done
In an attempt to remove some of the "un" from "unknown," Hillstrom et al. collected 200 mating pairs of Polydrusus sericeus weevils -- which they describe as "the second most abundant invasive weevil species in northern hardwood forests" -- from birch trees growing on the perimeter of the Aspen Face facility in Oneida County, Wisconsin (USA), after which they fed them leaves taken from the birch, aspen and maple trees growing within either the facility's ambient-air rings or its CO2-enriched rings (which were maintained at a target concentration of 560 ppm) under controlled laboratory conditions throughout the entire summer of 2007, while they closely monitored parameters related to weevil longevity and fecundity.

What was learned
The five researchers, all from the University of Wisconsin's Department of Entomology, report that feeding the weevils with foliage produced on trees in the CO2-enriched FACE plots had no affect on male longevity, but that it reduced female longevity by 19%. And they state that "Polydrusus sericeus egg production rate declined by 23% and total egg production declined by 29% for females fed foliage produced under elevated CO2 compared with ambient CO2."

What it means
In light of their several findings, as well as the continued upward trend in the air's CO2 content, Hillstrom et al. conclude that "concentrations of elevated CO2 above 500 ppm have the potential to decrease P. sericeus populations by reducing female longevity and fecundity," which should be particularly good news for the northern hardwood forests of North America.

Reviewed 27 October 2010