Thursday, August 7, 2008 - 4:20 PM

COS 97-9: Herbivory impacts inherited variation in herbivore performance via induced changes to plant quality: A case for niche construction

Adam Ehmer1, Matthew Forister2, and Douglas Futuyma1. (1) Stony Brook University, (2) University of Nevada, Reno


Niche construction occurs when organisms modify their environment in a way that changes natural selection on themselves. Multivoltine herbivorous insects are particularly susceptible to niche construction because they affect their resource base quantitatively and qualitatively over the course of their growing season. Specifically, the act of herbivory can induce changes in plant quality that impact the performance of subsequent herbivores. Niche construction can be an important evolutionary force if the traits that contribute to niche construction and the traits that respond to niche construction are genetically variable and under selection. The Colorado potato beetle, Leptinotarsa decemlineata, is a multivoltine herbivore that feeds on crops, weeds, and native plants in the genus Solanum. The effects of prior beetle herbivory, through changes in plant quality, on the performance of a later generation of beetles were examined in a quantitative genetic framework using a nested paternal half-sibling design. Adult beetles were used to damage potato plants that were then feed to larvae that were measured for several performance traits.  Main effects of prior herbivory on performance, additive genetic variation, maternal effects, genotype by environment interactions, and genetic correlations among traits were estimated from these data.

Beetles that fed on foliage from previously damaged plants gained less weight as larvae, took longer to develop, and eclosed at lighter weights compared to beetles that fed on undamaged control plants.  There was no significant additive genetic variation for any trait measured, but maternal effects were significant for most traits.  The magnitude of maternal effects were greater for beetles that fed on foliage from previously damaged plants, suggesting that niche construction could affect evolutionary responses both by altering natural selection and the expression of inherited variation.  Genetic correlations suggest that traits contributing to niche construction are positively correlated with those that are sensitive to niche construction.