Multigenerational Consequences Of Aphid Size On Offspring Phenotype And Reproduction

In many organisms, phenotype and fitness are strongly influenced by both current environmental factors and maternal effects. The low genetic variation, high phenotypic plasticity, and telescoping generations seen in aphids permit us to investigate the relative importance and potential interaction of maternal and current environments on phenotype. Although past studies have identified an influence of maternal host plant on offspring phenotype and reproduction in aphids, few have demonstrated the potential for these maternal effects to also interact with the aphid's current environment. By rearing multiple generations of Aphis nerii (Fonscolombe) (Hemiptera: Aphididae) on their host common milkweed, Asclepias syriaca (L.) (Apocynaceae), we tested the relative influence and interaction of both maternal and current environmental effects of crowding and plant quality on aphid body size and reproduction. Our results indicate that aphid body size increased with current plant quality and decreased with aphid density in both generations, with an additional direct, positive relationship between body size and fecundity. We did not find evidence for adaptive maternal effects, e.g., production of fewer, larger, offspring by stressed mothers. Instead, poor maternal environments constrained aphid body size and reproduction. Importantly, these adverse maternal effects were only seen in offspring where subsequent nymph population growth was allowed to increase unchecked, likely reducing available resources. Our study thus demonstrates that the significance of maternal effects in aphid development and reproduction can depend on current resource availability, shaping the phenotype and fecundity of offspring under stressful conditions. Incorporating this framework for how aphid body size and reproduction respond to current and maternal environments may improve predictions for how aphid population growth is impacted by resource limitation across generations.