90.3 Friday, Jan. 6 Experimentally decoupling reproductive investment and energy storage to investigate the functional basis of life-history trade-offs COX, Robert M*; CALSBEEK, Ryan; University of Virginia; Dartmouth College email@example.com
The trade-off between reproduction and survival is central to life-history theory, but we currently know little about the physiological mechanisms that link these two components of fitness. We have previously shown that the elimination of reproduction via surgical ovariectomy (OVX) dramatically increases the survival of brown anole lizards (Anolis sagrei) in the wild. This survival advantage persists even after the conclusion of the reproductive season and is accompanied by increases in growth, fat storage, hematocrit, and immune function. Collectively, these results suggest that reproduction leaves females energetically compromised and unable to fully support maintenance functions that could otherwise improve their survival. To test this hypothesis, we assigned females to three treatment groups: (1) bilateral OVX, (2) unilateral OVX, and (3) intact SHAM control. As predicted, unilateral OVX induced levels of reproductive output, growth, and fat storage that were statistically intermediate between SHAM and bilateral OVX. Survival followed a similar stepwise decrease from bilateral OVX (0.33) to unilateral OVX (0.31) and SHAM (0.26), but these differences were not significant. At the conclusion of the breeding season, we decoupled these reproductive manipulations from their effects on energy storage by dividing the survivors from each group into two further treatments: (1) surgical excision of abdominal fat bodies, or (2) sham surgery (fat bodies intact). Although this manipulation had a strong and persistent effect on energy stores, it did not influence survival in any of the three reproductive treatments. This suggests that the energetic savings of reduced reproductive investment is insufficient to fully explain the accompanying increase in survival in this species.