D3408: Effects of resource quality and landscape complexity on body size plasticity

Insects that subsist in agricultural landscapes are exposed to rapidly changing environments. The ability of these species to adapt to temporally varying local resources, such as presence and quality of food sources, may influence their ability to persist in local environments. The ability of a trait to change within just a few generations, trait plasticity, may be influenced by the local landscape composition of that population. It was previously shown in plants that certain intraspecific traits, like induction of defensive compounds, may be differentially plastic based on their landscape of origin. Here, we ask whether body size plasticity in insects varies based on local landscape composition. The seedcorn maggot, Delia platura (Meigen) (Diptera: Anthomyiidae), is an economically important pest of large-seeded crops. As a generalist, it can utilize a wide range of food sources – making it ideal for studying how food quality and landscape composition may affect trait plasticity. In field-collected flies, we found both pupal and adult body size increasing as agricultural land cover increases. To determine if there is varying body size plasticity in dependence of landscape composition, we ran a lab experiment with flies from ten sites of varying landscape complexity, who were fed higher and lower nutritional quality diets. We found that flies fed the higher-quality food were larger, and those originating from more highly agricultural landscapes had a greater difference in body size between offspring fed the different diets, indicating that increased instability of agricultural landscapes results in greater trait plasticity in local populations.