Lancaster L T, Hazard L C, Clobert J, Sinervo B R
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA, USA.
J Evol Biol. 2008 Mar;21(2):556-65. doi: 10.1111/j.1420-9101.2007.01478.x. Epub 2008 Jan 3.
Life history trade-offs are often hierarchical with decisions at one level affecting lower level trade-offs. We investigated trade-off structure in female side-blotched lizards (Uta stansburiana), which exhibit two evolved strategies: yellow-throated females are K-strategists and orange-throated are r-strategists. Corticosterone treatment was predicted to differentially organize these females' reproductive decisions. Corticosterone-treated yellow females suppressed reproduction but survived well, and augmented egg mass without decreasing clutch size. Conversely, corticosterone enhanced mortality and reproductive rates in orange females, and increased egg mass only after lengthy exposure. Corticosterone did not affect post-laying condition, suggesting that corticosterone increased egg mass through enhanced energy acquisition (income breeding). Corticosterone enhanced survival of lightweight females, but decreased survival of heavy females, introducing a foraging vs. predation trade-off. We conclude that rather than being a direct, functional relationship, observed trade-offs between offspring size and number represent evolved differences in hierarchical organization of multidimensional trade-offs, particularly in response to stress.
生活史权衡通常具有层级性，一个层面的决策会影响较低层面的权衡。我们研究了雌性侧斑蜥蜴（Uta stansburiana）的权衡结构，它们展现出两种进化策略：喉部黄色的雌性是K策略者，喉部橙色的是r策略者。预计皮质酮处理会使这些雌性的生殖决策产生差异。经皮质酮处理的黄色雌性抑制了繁殖，但存活良好，增加了卵的质量且未减少窝卵数。相反，皮质酮提高了橙色雌性的死亡率和繁殖率，且只有在长时间暴露后才增加卵的质量。皮质酮不影响产卵后的状况，这表明皮质酮通过增强能量获取（收入繁殖）来增加卵的质量。皮质酮提高了轻体重雌性的存活率，但降低了重体重雌性的存活率，引入了觅食与被捕食之间的权衡。我们得出结论，后代大小与数量之间观察到的权衡并非直接的功能关系，而是多维权衡层级组织中进化差异的体现，尤其是对压力的反应。
