Scale dependence in the preference-performance relationship of the specialist seed predator Schinia florida

Oviposition choice and larval performance are essential metrics that determine the fitness outcomes in plant-herbivore interactions. The long-standing preference-performance hypothesis predicts that parents should choose to oviposit on plants that maximize offspring performance. While this hypothesis sometimes holds true, there are often conflicting results. Here we seek to explain variation in the preference-performance relationship by investigating the mechanistic drivers underlying preference and performance and how the relationship changes across scales. Accordingly, we measured a suite of 130 plant traits, most of which were plant secondary metabolites. We also measured oviposition choice and larval performance using the seed predator moth Schinia florida and the common evening primrose Oenothera biennis at the level of whole plants and plant parts (flower buds vs. fruits). Seven traits predicted both adult oviposition preference and larval performance, all seven traits had inverse relationships indicating a negative preference-performance relationship. Despite this, we found no preference-performance relationship across individual plants, and within plants moths preferred to oviposit on buds over fruits and showed concordant higher performance on buds. The negative preference-performance relationship across individual traits may be explained by this specialist moth’s use of toxic traits to locate host plants. Supporting this explanation, we found that plant traits were weaker predictors of preference and performance within plants, where host finding is not important, allowing moths to choose the best oviposition sites between tissues.