Environmental quality predicts optimal egg size in the wild

Parents can maximize their reproductive success by balancing the trade-off between investment per offspring and fecundity. According to theory, environmental quality influences the relationship between investment per offspring and offspring fitness, such that well-provisioned offspring fare better when environmental quality is lower. A major prediction of classic theory, then, is that optimal investment per offspring will increase as environmental quality decreases. To test this prediction, we release over 30,000 juvenile Atlantic salmon (Salmo salar) into eight wild stream environments, and we monitor subsequent growth and survival of juveniles. We estimate the shape of the relationship between investment per offspring (egg size) and offspring fitness in each stream. We find that optimal egg size is greater when the quality of the stream environment is lower (as estimated by a composite index of habitat quality). Across streams, the mean size of stream gravel and the mean amount of inc...

亲本可通过权衡单子代投入与繁殖力之间的关系，最大化自身繁殖成效。依据经典生活史理论，环境质量会调控单子代投入与子代适合度间的关联：当环境质量越低时，获得更多资源供给的子代适合度越高。据此，经典理论的核心预测之一为：单子代最优投入将随环境质量的下降而升高。为验证该预测，我们将逾3万尾幼年大西洋鲑（Salmo salar）投放至8个野生溪流生境中，并对幼鲑后续的生长与存活情况开展监测。我们估算了每个溪流生境中，单子代投入（即卵粒大小）与子代适合度之间的函数形态。研究发现，以生境质量综合指数评估的溪流环境质量越低，最优卵粒尺寸越大。跨溪流分析显示，溪流砾石平均粒径与...