PARENT SESSION
Oral Session #18: Predator-Prey Interactions: Plants and animals. Presiding: B. Goodwin.
Monday, August 6, 2001. 1:00 PM to 5:00 PM. Hall of Ideas I.
Effects of prey diet, temperature and prey abundance on consumption, weight gain and survival of a lady beetle predator.
Ball Dobley, Karen1, Stamp, Nancy1, 1
ABSTRACT- Plant chemicals sequestered in their prey can sometimes negatively affect insect predators. Warmer temperatures and scarce prey can enhance these negative effects. No known studies have looked at all three factors of plant chemicals, temperature and prey abundance. This study tested combined effects of milkweed plant chemicals, temperature and prey abundance on consumption, weight gain and survival of a lady beetle predator. Lady beetles were fed milkweed aphids (containing plant chemicals), flies, or multiple prey types, and were raised under two thermal regimes and two prey abundance levels. The average number of prey eaten per day by the beetles was determined as well as weight gained and survival. The data were analyzed using ANOVA and it was found that beetles fed milkweed aphids ate a similar number of prey as beetles fed the other prey diets but gained significantly less weight and experienced greater mortality. Including alternate prey increased survival and weight gain of beetles fed milkweed aphids. Warmer temperatures increased prey consumption by the predators and increased weight gained. With abundant prey, beetles consumed more prey and gained more weight than beetles fed a scarce level of prey. There were interactive effects: the effects of prey diet were a function of temperature and prey abundance. Plant chemicals in their prey may negatively affect lady beetle survival and weight gain and this affect is dependent on temperature and prey abundance.
KEY WORDS: Plant chemicals, Lady beetles, temperature, prey abundance