MERRY, J.W.*; KEMP, D.J.; SCOW, A.M.; VIVAS, R.F.; RUTOWSKI, R.L.; Arizona State University; Arizona State University; Arizona State University; Arizona State University; Arizona State University: The effects of family and larval host plant quality on vision in the Orange Sulphur Butterfly, Colias eurytheme

Understanding the factors that affect variation in a trait can provide insight into how that trait is expressed within a population, as well as how a trait may change over evolutionary time. Sensory organs are crucially important to behavior in animals, and variation in sensory system performance will thus be a key determinant of their fitness. Therefore, animals may be under selection to maintain the performance of their sensory systems in the face of poor growing conditions. We conducted a rearing experiment in which we subjected larvae from 38 full sib families to one of two different food quality treatments. We then raised the animals to adulthood and measured two indicators of visual capability: eye size and facet diameter. We predicted that animals on the poor diet would maintain eye size and thus maintain their visual capabilities. Thus, animals raised on poor quality food would have proportionally larger eyes than animals on high quality diets, despite having smaller body size. We found that larval diet strongly influenced body size in both sexes, however eye size scaled allometrically with body size regardless of the food treatment. There were minimal family-driven differences in eye size, despite the fact that other characters on these same individuals did have significant heritabilities. Therefore, these butterflies do not appear to maintain their vision when faced with harsh growing conditions. We discuss whether this may be due to a constraint preventing such an accommodation from occurring, or simply lack of selection favoring this response.