Variation in Elemental Composition (N and P) of Host Plants and the Consequences for Herbivore PerformanceEPA Grant Number: U915789
Title: Variation in Elemental Composition (N and P) of Host Plants and the Consequences for Herbivore Performance
Investigators: Huberty, Andrea F.
Institution: University of Maryland
EPA Project Officer: Lee, Sonja
Project Period: August 1, 2000 through August 1, 2003
Project Amount: $92,137
RFA: STAR Graduate Fellowships (2000) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Biology/Life Sciences , Fellowship - Entomology
The objective of this research project is to determine the effects of nitrogen (N) and phosphorus (P) inputs on the performance, stoichiometry, and life history patterns of the monophagous planthoppers, Prokelisia dolus and Prokelisia marginata, and their host plant Spartina alterniflora.
To investigate the performance of the planthoppers when reared on different elemental compositions of their host plant, a 4x4 factorial was conducted for each species in the laboratory. Four different levels of N (0, 10, 30, and 60 g / m2) and 4 different levels of P (0, 2, 6, 12 g / m2) were used to establish the 16 treatments. Previous experiments conducted by members of the investigator's laboratory supported the use of these fertilization levels. However, all plants at the highest N fertilization level died due to fertilization burning before the establishment of the planthoppers. Height dried biomass of the plants were measured to establish the efficacy of the treatments, and the percent N and percent P of each treatment was determined. Planthoppers were reared on the plants from day 2 to adulthood, and tibial length (as an index of body size), development time, and growth rate (mm of tibial length gained/day) were determined. The insects were also analyzed to determine the percent N and percent P content to investigate the relationship between the plant and insect elemental composition. A field fertilization experiment will be conducted on a salt marsh in Tuckerton, NJ to investigate the effect of N and P fertilization on Spartina, as well as the planthoppers, to determine the effect of N and P fertilization run-off on the phytophagous insect community and how increases in fertilization may play a role in the life history patterns of the Prokelisia species. Also, field and experimental insects will be analyzed to determine if there is a trade-off between compensatory feeding ability (cibarial pump musculature) and migratory ability (flight musculature) in each species and wingform (brachypter and macropter), and if the amounts of these muscles vary with plant quality and insect stoichiometry (N and P content). Flight capabilities of these two species may be a direct response to their respective ability to process nutrient-deficient food. The elemental composition of each species and the compatibility of this composition with the stoichiometry of their food may be an important factor in the results of this experiment. Throughout these experiments the insects' elemental composition will also be monitored to determine if these species have homeostatic stoichiometries.
A better understanding of the effects of N and P on host plants and herbivor performance is expected.