Meeting Abstract

26.2  Friday, Jan. 4  Comparative Effects of Adult Food Limitation on Butterfly Life Histories BOGGS, C.L.*; NIITEPOLD, K.; PEREZ, A.; Stanford University; Stanford University; Stanford University cboggs@stanford.edu

Change in resource allocation patterns in response to variation in food acquisition provides a mechanistic basis for understanding observed life history responses to variation in food availability. Organisms respond differently to changes in food quantity vs. quality, as demonstrated empirically and theoretically, using conceptual structures such as resource congruence, stoichiometry and the geometric framework. Here we examine the life history effects of realistic changes in the quantity of food available and connect lab experiments to field observations, using butterflies as a model system. Variance in per capita flower availability results from weather and land use patterns, and can lead to prolonged nectar limitation. In butterflies, adult food limitation generally doesn’t affect lifespan, but can lead to reduced fecundity. We extend work on allocation to reproduction under nutrient stress by asking how such stress affects fecundity, egg mass and composition as a function of age in two species with contrasting life histories, hence physiological demands. The larvae of Speyeria mormonia diapause without feeding and hence the eggs are expected to have a greater energetic provisioning requirement than eggs of Colias eurytheme. Likewise S. mormonia has a higher use of adult food in egg production. Consistent with these traits, under laboratory conditions, S. mormonia’s eggs are heavier, and fecundity decreases to a greater extent under nutrient stress. Nonetheless, S. mormonia does not defend egg mass or egg energy stores under nutrient stress, although C. eurytheme does. We also compare female performance under stress in the lab with that in the field for S. mormonia.