Data from: Experimentally decoupling reproductive investment from energy storage to test the functional basis of a life-history tradeoff

The ubiquitous life-history trade-off between reproduction and survival has long been hypothesized to reflect underlying energy-allocation trade-offs between reproductive investment and processes related to self-maintenance. Although recent work has questioned whether energy-allocation models provide sufficient explanations for the survival cost of reproduction, direct tests of this hypothesis are rare, especially in wild populations. This hypothesis was tested in a wild population of brown anole lizards (Anolis sagrei) using a two-step experiment. First, stepwise variation in reproductive investment was created using unilateral and bilateral ovariectomy (OVX) along with intact (SHAM) control. Next, this manipulation was decoupled from its downstream effects on energy storage by surgically ablating the abdominal fat stores from half of the females in each reproductive treatment. As predicted, unilateral OVX (intermediate reproductive investment) induced levels of growth, body condition, fat storage and breeding-season survival that were intermediate between the high levels of bilateral OVX (no reproductive investment) and the low levels of SHAM (full reproductive investment). Ablation of abdominal fat bodies had a strong and persistent effect on energy stores, but it did not influence post-breeding survival in any of the three reproductive treatments. This suggests that the energetic savings of reduced reproductive investment do not directly enhance post-breeding survival, with the caveat that only one aspect of energy storage was manipulated and OVX itself had no overall effect on post-breeding survival. This study supports the emerging view that simple energy-allocation models may often be insufficient as explanations for the life-history trade-off between reproduction and survival.

繁殖与存活之间普遍存在的生活史权衡（life-history trade-off）长期以来被假设为反映了繁殖投入与自我维持相关过程之间的潜在能量分配权衡。尽管近期研究对能量分配模型能否充分解释繁殖带来的存活成本提出了质疑，但直接验证该假说的研究仍较为匮乏，尤其是在野生种群中。本研究针对野生褐安乐蜥（Anolis sagrei）种群开展了两步实验以验证该假说：首先，通过单侧卵巢切除术（unilateral ovariectomy, OVX）、双侧卵巢切除术以及假手术（SHAM）对照，构建了梯度变化的繁殖投入水平；其次，为排除该操作对能量储备的下游影响，研究人员对每种繁殖处理组中半数雌性个体实施了腹部脂肪体切除手术。正如实验预期，单侧卵巢切除术组（对应中等繁殖投入水平）个体的生长速率、身体状况、脂肪储存量以及繁殖季存活率均处于双侧卵巢切除术组（无繁殖投入）的高水平与假手术组（完全繁殖投入）的低水平之间。腹部脂肪体切除手术对能量储备产生了显著且持久的影响，但并未对三种繁殖处理组的繁殖后存活率造成任何影响。这表明降低繁殖投入所节省的能量并未直接提升繁殖后存活率，但需注意本研究仅操控了能量储存的一个维度，且卵巢切除术本身对繁殖后存活率并无整体影响。本研究支持了新兴观点：简单的能量分配模型往往不足以解释繁殖与存活之间的生活史权衡。