(1st Place) Three's a crowd: How density and temperature guide nutrient regulation in a phenotypically plastic herbivore

Nutrition and temperature are two factors that affect the performance and fitness of organisms. These factors also vary over time and location and thus organisms must adapt to the changing environment. One way organisms adapt to environmental variation is through plastic traits. A prominent example of which is the density-dependent phenotypic plasticity of the desert locust, Schistocerca gregaria. While Nutritional regulation has been heavily studied in this organism, this research only contains treatments with a singular locust. However, gregarious locusts exist in groups which drastically changes the ecological landscape. Therefore, the role of density should be investigated to fully understand nutritional regulation in locusts. This study aims to investigate if density affects macronutrient regulation and to identify differences in feeding behaviour across temperatures. To address these aims, final instar S. gregaria were placed into an arena: (i) individually, or with two conspecifics (ii) each separated by mesh or (iii) with no physical restrictions. Individuals were subjected to choice or no-choice experiments in ambient temperatures of 30°C or 34°C. We found that the protein-carbohydrate intake target was robust to environmental variation with all treatments regulating to a ratio of 1P:1C. However, the regulation strategy employed varied. At 30°C regulation differed by phenotype whereas at 34°C the strategy was consistent across densities. Interestingly, solitary nymphs had the same weight gain and total consumption across temperatures. These results suggest that solitary nymphs are more robust to environmental change and that, in high temperatures, phenotypic differences in nutritional regulation are not present.