Local host plants and diet mixing: Effects of plant chemistry on a generalist herbivore at the population level

Monday, November 11, 2013: 9:24 AM
Meeting Room 10 AB (Austin Convention Center)
Marion Le Gall , Department of Entomology, Texas A&M University, College Station, TX
Spencer T. Behmer , Department of Entomology, Texas A&M University, College Station, TX
Two hypotheses are usually advanced to explain why generalist herbivores benefit from diet mixing. The first hypothesis suggests that diet mixing allow generalist insects to acquire a balance blend of nutrients. The second hypothesis proposes that diet mixing allow generalist to deal with plant defenses by keeping the intake of individual toxins low. Both hypotheses have received some support. In this study we investigate the effect of the relationship between nutrient and allelochemical on performance and physiology.  Grasshoppers were collected from two wild populations and reared until the 6th instar on: 1) the most commonly eaten forb species, 2) the most commonly eaten grass species, and 3) a combination of these two.  All plant material was collected in the field and flash frozen to preserve the chemical integrity of each plant. For each plant species, we also measured protein, carbohydrate, alkaloids, phenolic and terpenoid content. Grasshoppers were presented the plant material in ground form and food consumption, growth, development plus body lipid levels were measured. We interpret our results in the context of plant secondary metabolites detoxification and discuss their significance for the field of nutritional ecology.