Meeting Abstract
Sodium is an essential micronutrient that is required for muscle and neural function in animals. Although this element has historically been limited in availability for terrestrial herbivores, humans have greatly increased the amount of available sodium, especially in northern climates where sodium chloride is used to de-ice roads. Previous research, using butterfly larvae as a model, has shown that moderate increases in sodium appear to be beneficial (i.e. they are able to invest more in brain and muscle tissue), but high sodium levels are toxic. However, it is unknown at what sodium concentrations we will see these apparent benefits or toxicities, and how sodium affects other life history traits, such as development time and fecundity. Furthermore, how much genetic variation exists for sodium-dependent traits or survival at toxic sodium levels is also unclear. This knowledge is essential to predict how butterflies may respond to these anthropogenic changes in nutrient levels. As a first step to answer these questions, we reared larvae from over 20 full sibling families of the cabbage white butterfly, Pieris rapae, on diets with 6 different concentrations of sodium. We measured survival, development time, adult body size, eye size as a proxy for investment in neural tissue, and amount of protein in flight muscles as a proxy for investment in muscle tissue. From this, we will be able to estimate broad-sense heritability for these traits and the shape of the reaction norm across the different sodium levels. The results of this experiment will show the relationship between sodium concentration and these butterfly traits, and also determine at what levels road salt application may exert selection on roadside feeding butterflies.
