Predator-induced transgenerational phenotypic plasticity in the cotton aphid

Transgenerational phenotypic changes, whereby offspring have an altered trait or a distinct alternate phenotype, frequently occur in response to increased maternal predation risk. The cotton aphid, Aphis gossypii (Glover), is unique, however, as offspring consist of four distinct phenotypes ("normal" light green apterae, "normal" dark green apterae, "dwarf" yellow apterae, and alatae), all with divergent life history patterns and resulting population dynamics. Here, we show that increased predation risk induces transgenerational phenotypic changes in cotton aphids. When exposed to search tracks from larval or adult convergent ladybird beetles, Hippodamia convergens Guérin-Méneville, cotton aphids produced greater numbers of winged offspring. In a subsequent experiment, apterous and alate individuals on clean plants were found to have primarily normal and dwarf offspring, respectively. We suggest that elevated predation risk may cause phenotypic changes in aphids over multiple generations, resulting in a more precipitous decline in herbivore populations than could be explained solely by increased predation rates.