Related Papers

Cox, R.M., and R. Calsbeek. 2010. Severe costs of reproduction persist in Anolis lizards despite the evolution of a single-egg clutch. Evolution 64: 1321-1330.

Cox, R.M., E.U. Parker, D.M. Cheney, A.L. Liebl, L.B. Martin, and R. Calsbeek. 2010. Experimental evidence for physiological costs underlying the trade-off between reproduction and survival. Functional Ecology 24: 1262-1269.

Cox, R.M. 2006. A test of the reproductive cost hypothesis for sexual size dimorphism in Yarrow's spiny lizard, Sceloporus jarrovii. Journal of Animal Ecology 75: 1361-136.

Figure 1. Experimentally eliminating reproduction (OVX) increases survival relative to reproductive (SHAM) females. By measuring energetics and maintenance and quantifying survival of OVX and SHAM under replicated, whole-island manipulations of the predation regime, we can experimentally test the physiological and ecological mechanisms that structure this fundamental trade-off.

How does current reproductive investment impact survival and future reproduction?

Classic life-history theory posits that investment in reproduction compromises survival. But what is the functional basis of this trade-off? Which aspects of reproduction render it costly? And is this trade-off generated by intrinsic sources of mortality, such as physiological maintenance, or by extrinsic ecological factors, such as predators?

We are addressing these questions by simultaneously manipulating the physiological basis and the ecological context of this trade-off in wild lizard populations. For example, by eliminating reproduction via surgical ovariectomy, we discovered that brown anole lizards suffer extreme reductions in growth, locomotor performance, and survival due to reproduction (Cox & Calsbeek 2010). Our experiments have also revealed pronounced physiological costs of reproduction, including reductions in energy storage, immune function and hematocrit (Cox et al. 2010). We also recently developed a powerful new technique for measuring natural selection in response to manipulations of the entire predation regime on replicate island populations of anoles (Calsbeek & Cox 2010). We are now combining this experimental method with manipulations of reproduction to test whether susceptibility to predation contributes to the survival cost of reproduction (Fig. 1).