PARENT SESSION
Poster Session #55: Plant-Animal Interactions II.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Heterogeneity in trophic systems: consequences of variable leaf quality along an elevational gradient .

Yarnes, Christopher^*,1, Boecklen, William¹, ¹ New Mexico State University, Las Cruces, NM

ABSTRACT- There has been much recent interest in abiotic heterogeneity mediating plant-insect interactions. We tested two hypotheses that together predict the consequences of abiotic heterogeneity for trophic systems. The atmospheric deposition hypothesis predicts a greater abundance of available nutrients at higher elevations, due to atmospheric nutrient deposition from increased levels of rain, clouds and fog. The carbon-nutrient balance hypothesis states concentrations of carbon-based secondary metabolites used in herbivore defense will decrease in response to increased nutrient availability, as fixed carbon is preferentially allocated for growth. This can result in heterogeneous plant quality and significantly affect population dynamics at higher trophic levels. We examined Gambel's oak, Quercus gambelii Nutt., along an elevational gradient under two fertilization regimes in order to investigate the effects of heterogeneity within (nutrient) and between (abiotic) elevational sites and its effects upon plant quality, associated herbivores and parasitoids. Leaf-miner, Phyllonorycter sp. (Lepidoptera: Gracillariidae), densities were significantly higher at the lowest elevation site and exhibited a significant site x treatment interaction across elevations. Larval performance and mortality rates varied with fertilization treatment level and elevation. Preliminary examination of nutrient concentration and secondary metabolites also suggests considerable variation with both experimental factors.

KEY WORDS: heterogeneity, trophic, Quercus gambelli , leaf-miner