Ecology. 2014 Apr;95(4):882-96. doi: 10.1890/13-1434.1.
An aspect of life history that has seen increasing attention in recent years is that of strategies for financing the costs of offspring production. These strategies are often described by a continuum ranging from capital breeding, in which costs are met purely from endogenous reserves, to income breeding, in which costs are met purely from concurrent intake. A variety of factors that might drive strategies toward a given point on the capital-income continuum has been reviewed, and assessed using analytical models. However, aspects of food supply, including seasonality and unpredictability, have often been cited as important drivers of capital and income breeding, but are difficult to assess using analytical models. Consequently, we used dynamic programming to assess the role of the food supply in shaping offspring provisioning strategies. Our model is parameterized for a pinniped (one taxon remarkable for the range of offspring-provisioning strategies that it illustrates). We show that increased food availability, increased seasonality, and, to a lesser extent, increased unpredictability can all favor the emergence of capital breeding. In terms of the conversion of energy into offspring growth, the shorter periods of care associated with capital breeding are considerably more energetically efficient than income breeding, because shorter periods of care are associated with a higher ratio of energy put into offspring growth to energy spent on parent and offspring maintenance metabolism. Moreover, no clear costs are currently associated with capital accumulation in pinnipeds. This contrasts with general assumptions about endotherms, which suggest that income breeding will usually be preferred. Our model emphasizes the role of seasonally high abundances of food in enabling mothers to pursue an energetically efficient capital-breeding strategy. We discuss the importance of offspring development for dictating strategies for financing offspring production.
近年来，人们越来越关注生命史的一个方面，即后代生产成本的融资策略。这些策略通常可以用一个连续体来描述，从纯粹依靠内源性储备来满足成本的资本繁殖，到纯粹依靠同期摄入来满足成本的收入繁殖。已经综述了许多可能导致策略向资本-收入连续体上特定点的因素，并使用分析模型进行了评估。然而，食物供应的各个方面，包括季节性和不可预测性，通常被认为是资本和收入繁殖的重要驱动因素，但使用分析模型很难评估。因此，我们使用动态规划来评估食物供应在塑造后代供应策略中的作用。我们的模型是针对鳍足类动物（一类以其展示的一系列后代供应策略而闻名的分类群）进行参数化的。我们表明，食物供应的增加、季节性的增加，以及在较小程度上，不可预测性的增加，都可以有利于资本繁殖的出现。就能量转化为后代生长而言，与资本繁殖相关的较短的护理期在能量效率上要远远高于收入繁殖，因为较短的护理期与投入到后代生长的能量与用于父母和后代维持代谢的能量的比例更高有关。此外，目前在鳍足类动物中，资本积累没有明显的成本。这与关于恒温动物的一般假设形成对比，恒温动物的一般假设表明，收入繁殖通常是首选。我们的模型强调了季节性高食物丰度在使母亲能够追求能量效率高的资本繁殖策略方面的作用。我们讨论了后代发育在决定后代生产融资策略方面的重要性。
