Elevated CO2 will not select for enhanced growth in white spruce despite genotypic variation in response

The effect of elevated atmospheric CO2 on plant growth has been well-documented in the literature. However, few Studies have quantified intra-specific genetic variation in growth response, and the potential for natural and artificial selection to act upon this variation. This Study examined intra-specific variation in growth response to elevated CO2 In 29 genotypes of white spruce (Picea glauca), a widely distributed and economically important species of the boreal forest region in North America. Trees were exposed to either ambient (370 mu L L-1) or twice-ambient CO2 (740 mu L L-1). The opportunity for selection (i.e. the relative variation in fitness) was determined Lit low and high CO2 levels with size as a measure or fitness and heritability of this variation determined. There was considerable variation among the genotypes in size and response to elevated CO2. The increase in mass Lit elevated CO2 ranged from 23% to 108% depending upon genotype. In spite of this variation, the genetic correlation between the two environments approached unity, as genotype variance was Much greater than the genotype x CO2 variance. Elevated CO2 had no effect on heritability of the size-related traits we examined, and either had no effect on opportunity for selection, or decreased it. We conclude that selection at elevated atmospheric CO2 is unlikely to increase mean plant size in White Spruce beyond that observed for present day populations grown Lit elevated CO2, despite the substantial genetic variation in CO2 response displayed by this species. (C) 2008 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.