Life history theory predicts that organisms should modify their allocation of resources to different parts and functions in order to maximize fitness. In perennial plants, genotype and environmental conditions are expected to cause variation in resource allocation patterns. Such variation, in turn, could have important impacts on herbivores that prefer particular genotypes or plant parts. Thus, identifying the causes and consequences of variation in resource allocation is critical to our understanding of life history strategies. In a growth chamber experiment, we planted 20 genotypes of the common milkweed Asclepias syriaca and measured 13 above- and below-ground traits to estimate differences in resource allocation due to genotype. In a parallel field experiment using the same 20 genotypes, we manipulated the abundance of the specialist root herbivore Tetraopes tetraophthalmus, and tested for single and interactive effects of this treatment and plant genotype on allocation.
Results/Conclusions
We found that genotypes differed significantly in their overall allocation pattern, mostly due to variation in shoot dry weight, number of secondary roots, and number of root buds (a measure of clonal growth potential). Above-ground traits were highly positively correlated, whereas some below-ground traits exhibited trade-offs and were less integrated overall. In the field, root herbivores enhanced allocation to new stems, possibly by releasing bud dormancy, and this effect varied with plant genotype. By considering both genetic and environmental factors driving plant resource allocation, and then evaluating the consequences of such variation, this work represents an initial attempt to understand plant allocation strategies in a community context.
