Meeting Abstract

81.1  Wednesday, Jan. 6  Resource supplementation reduces trade-offs in male, but not female, sagebrush lizards RUIZ, M.A.; Indiana University, Bloomington mayruiz@indiana.edu

The dietary resources available to organisms in their natural environment determine the energy available at a given time. This energy is essential for an organism to carry out the cellular processes required for survival and reproduction. We thus considered the effect of food availability on immune function and reproductive physiology in a field population of sagebrush lizards, Sceloporus graciosus. In a series of field studies, we manipulated diet (with supplemental feedings) of males (in 2008) and females (in 2009) in a natural population. Additionally, we increased testosterone (T) levels with a non-invasive dermal patch in male lizards. After a week of manipulation, we collected blood from the postorbital sinus for use in immune and hormone assays. We determined immune response by calculating the bacterial killing capability of collected plasma exposed to E. coli ex vivo. We determined reproductive investment by assessing reproductive hormone concentrations (T in males) through radioimmunoassay and by measuring morphological changes of female reproductive characteristics. We observed an interactive effect of food availability and T-patch on immune function in males, with food supplementation increasing immunity in T-patch lizards. Furthermore, males with supplemental food had higher circulating testosterone than controls. In females, food supplementation did not enhance immune function nor did it seem to have an immediate affect on female reproduction. Collectively, this study shows that the energetic state of the animal plays a role in modulating the interactions among immunity and reproduction and that the sexes differ in the distribution of these tradeoffs in sagebrush lizards and likely other species.