PARENT SESSION
Poster Session #56: Animal Population and Community Ecology II.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

The effects of predation risk and resource addition on fitness components of nymphal Ageneotettix deorum .

DANNER, BRADFORD^*,1, JOERN, ANTHONY¹, ¹ University of Nebraska-Lincoln, Lincoln, NE

ABSTRACT- Fitness components of phytophagous insects are highly dependent on multiple environmental conditions. The effect of resource quality, water availability and temperature on the development and growth of several insects have been examined and discussed in laboratory experiments with the insect in question subjected to controlled conditions. Less understood perhaps is how predators can impact the growth and development of their insect prey, and how this role may potentially interact with other sources of variation, such as resource quality and quantity. Enclosure experiments were conducted under natural field conditions to detect and quantify the effects of predation risk from wandering spiders, resource quality, density and time on the development, growth, survival and reproductive output of Ageneotettix deorum, a common grasshopper found in North America. The potential presence of Lycosid spiders and fertilized vegetation affected both the rate of development and the final size of grasshoppers. However, fertilizer treatment had a greater effect on determining the rate at which development took place, while risk of predation impacted size of individuals over time. Grasshoppers growing in the absence of predation risk had a higher probability of survival. Reproductive output was estimated using ovariole dissections and follicular analyses on females that survived until the experiment was terminated. A greater number of reproductive events were recorded for females grown in the absence of predation risk. The effects of spider predation risk on the growth and development of A. deorum nymphs was less pronounced at higher grasshopper densities.

KEY WORDS: field experiment, grasshopper ecology, Nebraska sandhills grassland, predator-prey interaction