Effects of soybean foliage grown under elevated CO2 on the Japanese beetle, Popillia japonica (Newman).
O'Neill, Bridget*,1, Zangerl, Arthur1, DeLucia, Evan2, Berenbaum, May1, 1 University of Illinois, Urbana-Champaign, Urbana, IL, USA2 University of Illinois, Urbana-Champaign, Urbana, IL, USA
ABSTRACT- At the soybean free-air carbon-dioxide-enriched (SoyFACE) site, Japanese beetles (Popillia japonica (Newman) were twice as abundant on plants grown at projected future levels of elevated CO2. Increased abundance could reflect the fact that elevated CO2 increases foliar sugar content; sugars are feeding stimulants for P. japonica. To determine effects of consuming elevated CO2 plants on lifespan and fecundity, Japanese beetles in the laboratory were fed soybean leaves either grown in an elevated carbon dioxide atmosphere (550 ppm), grown in a control atmosphere (370 ppm), or supplemented with sugars (sucrose, glucose, and fructose) administered through their petioles, for the duration of their adult lives. Cages were checked daily for adult beetle mortality, and laying substrate was sifted weekly to allow counting of eggs and larvae. Adult lifespans of both male and female beetles were significantly prolonged on elevated-CO2 foliage; in addition, these females laid significantly greater numbers of eggs (p < 0.001). Increased egg production was at least in part attributable to increased longevity, as there was a significant correlation between eggs laid and total beetle days. There was no significant difference in egg production between females fed elevated levels of sugars and females fed either elevated CO2 or ambient leaves. Increased sugars had no effect on beetle longevity but may contribute to increased fecundity. Increased lifespan may be due to elevated levels of antioxidants in foliage resulting from exposure to elevated carbon dioxide.
Key words: Popillia japonica, Glycine max, elevated carbon dioxide, global change
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