Aspen leaf miner (Phyllocnistis populiella) oviposition site selection mediated by aspen (Populus tremuloides) extrafloral nectaries

Abstract

By impacting performance of individual offspring, oviposition site choice can have a large influence on female fitness; however, a female’s fitness is also impacted by her own survival and future reproductive potential. Factors influencing oviposition site selection include a female’s own predation risk and nutritional needs, as well as the performance of offspring. Trade-offs may occur when oviposition sites differ in their favorability for these fitness-related functions. Adults of the leaf-mining moth, Phyllocnistis populiella, forage at the extrafloral nectaries (EFNs) of quaking aspen, Populus tremuloides. Females are synovigenic and likely rely on adult nutrition for egg production; however, proximity to EFNs may be associated with reduced offspring survival. In a controlled experiment, when given the choice of oviposition on either a leaf with or without EFNs, P. populiella preferred leaves lacking EFNs. Seven years of field survey data revealed significantly higher oviposition and lower egg predation on leaves lacking EFNs. Aspen shoots with a higher proportion of leaves expressing EFNs experienced higher oviposition but no difference in egg predation. At the leaf level, eggs were overdispersed when at low to moderate densities, likely to decrease interference competition. Females mated multiply, and the acquisition of spermatophores through repeated matings may decrease P. populiella’s reliance on EF nectar for egg production. P. populiella appears to balance the trade-off between resource rich and high offspring performance sites by ovipositing in neighborhoods with a high proportion of leaves bearing EFNs, while preferring leaves lacking EFNs which experience lower egg predation.