PARENT SESSION
Contributed Oral Session 86: Herbivory: Genetic Variability in Insect - Plant Interactions
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 521 A, Level 5, Palais des congrès de Montréal

The effects of density and host plant species within and across generations on population dynamics of Aphis nerii, the milkweed-oleander aphid.

Zehnder, Caralyn^*,1, Hunter, Mark¹, ¹ University of Georgia, Athens, GA, USA

ABSTRACT- Non-Mendelian maternal effects, the effects of maternal phenotype or environment on offspring phenotype, have been documented in numerous taxa. By affecting offspring vital rates, maternal effects have the potential to influence population dynamics. However, relatively few studies have directly linked maternal phenotype or environment to offspring vital rates. Additionally, even fewer studies have compared the magnitude of across generation effects (i.e. maternal effects) to within-generation effects. We investigated experimentally the effects of maternal density and maternal host plant species on offspring survival, fecundity and alate formation in Aphis nerii, the milkweed-oleander aphid. Because of their telescoping generations, aphids are thought to be strongly influenced by maternal effects. In another set of experiments, we examined the effects of current density and host plant species (within generation effects) on aphid vital rates. Our results indicate that the effects of the current generation outweigh any impacts from the maternal generation. Maternal effects were relatively weak and had little or no impact on aphid vital rates. However, within-generation effects were very strong. Aphids exhibited density-dependent survival, fecundity and alate formation and these effects varied among the host plant species. These results indicate that while maternal effects have the potential to affect population dynamics, this potential is not always met. Additionally, in this system, within-generation effects were much stronger than maternal effects. Therefore, when studying maternal effects it is important to compare the relative strength of maternal vs. within-generation effects.

Key words: maternal effects, density dependence, aphids, plant quality