Meeting Abstract
Life history theory predicts that investment of acquired energetic resources to a particular trait denies those same resources from being allocated to a different trait. This constitutes the basis for life-history trade-offs, such as the ubiquitous trade-off between survival and fecundity, which is thought to result from differential allocation of resources to traits promoting survival and reproduction. Whole-organism performance traits, such as locomotor capacity, are key to fitness and fit within this framework. Such traits are typically energetically expensive, but few have integrated performance into life-history studies. We manipulated diet and allocation of resources to performance, via exercise training, to examine tradeoffs among endurance capacity, growth, immune function, secondary sexual characters (in males), and reproduction (in females). Captive green anole lizards were assigned to one of four treatment combinations across two factors (diet restricted or not and endurance trained on a treadmill or not) over the course of nine weeks: not-trained, unrestricted diet; not-trained, restricted diet; trained, unrestricted diet; and trained, restricted diet. To measure immune function we quantified immune organ masses, bacterial killing capacity of plasma, and the swelling response to phytohemagglutinin Results indicated that the combination of diet restriction and training dramatically suppressed reproduction and immune function, as well as growth and male secondary sexual characters. When individual factors were considered, diet restriction alone had a greater impact than training alone. We also explored potential hormonal mechanisms for the responses. Our results suggest that allocating energy into something as costly as immune function is dependent on resource availability and how those resources are allocated to other traits, including individual performance capacity.
