Terpenes and Genotype Choice by a Specialist Aphid in the Old-field Plant Species Solidago altissima Ray S Williams and Megan Avakian Appalachian State University Ray S Williams and Megan Avakian Appalachian State University

Thanks! Peter Blum Bryan Taylor Bess Smith Lara Katz Howells Family Jeff Williams Mike Madritch Jacob Pawley David Farrar Barkley Sive Appalachian State University Jen Schweitzer, Joseph Bailey University of Tennessee-Knoxville Megan Avakian

Background the lifeofyourtime.worldpress.com,

Crutsinger et al Intraspecific Variation

Potentially Important Plant Constituents for Insects Nitrogen C:N Water Allelochemicals Any or all could vary due to genotype and/or environment

Terpenes Langenheim 1994; Kalemba et al. 2001; Johnson et al. 2010; Williams and Avakian 2015

Solidago altissimaUroleucon nigrotuberculatum Study System

Questions Is the abundance of the specialist aphid Uroleucon nigrotuberculatum dependent on genotype and elevation in Solidago altissima? Which, if any, phytochemicals are related to aphid abundance?

Methods Spatially separated ramets of Solidago altissima were collected at 4 elevations- 260m, 585m, 885m and 1126m Plants were grown in pots for one year and cold hardened For 4 genotypes/elevation (= total of 16 genotypes) 3 cm rhizomes were propagated in standard soil mix with a root stimulator added One application of fertilizer was applied to plants grown under greenhouse conditions until transferred to the field at the ASU Biology Gilley Research Station

Deeded to ASU by Robert Gilley Approx ha Mixed land use, thus habitats ASU Biology Gilley Research Station (Ashe County, NC) Google Earth, courtesy of Mike Madritch

Replicated genotype/elevation monocultures (N=3) were planted in a randomly assigned common garden design 8 individuals were planted in each plot Total of 48 plots separated by 1 m

P= R 2 = 0.008

Insect Samples Visual survey of aphid abundance after 76 days in the field Vacuum sample of insect community Montanawildlifegardner.com

Leaf samples were taken for the analysis of water, N, C and volatile terpenes Non-destructive measure for biomass taken: Biomass (g) = (D 2 H*0.0022) (R 2 = 0.70, p < ) Leaf Chemistry Samples

Quantified 8 consistently scoreable mono- and sesquiterpenes identified using analytical standards and GC Mass-Spec Terpenes

Statistical Analyses A General Linear Model was used with genotype nested within elevation to partition effects Linear and Partial Least Squares Regression (PLSR) was used to relate terpenes to aphid abundance PLSR calculates latent variables explaining the best fit and creates a prediction value Regression of observed vs. predicted value provides correlation between phytochemicals and aphid abundance. PSLR is highly effective with co-linear data

Results

Abundance/g Biomass Genotype: P = Elevation: P = 0.934

Nitrogen C:N

Genotype Effect- Terpenes

No Genotype Effect- Terpenes

All Chemicals Nutrients Terpenes PSLR

Conclusions Because U. nigrotuberculatum abundance was affected by genotype but not elevation of origin, S. altissima exhibits phenotypic plasticity Differences among genotypes in terpenes, but not nutrients, shows that trait variation in this secondary metabolite class is more pronounced The relationship between suites of terpenes and insect abundance provides evidence that these phytochemicals contribute to aphid choice of genotypes

Questions?