Regulatory mechanisms and cost of reproduction

是什么阻止包括人类在内的动物随心所欲地生育出尽可能多的高质量后代？进化生物学给出的答案是，繁殖是有“成本”的，即在当前繁殖回合中增加投资的收益被当前条件、未来繁殖力和生存方面的成本所抵消。在鸟类中，大量证据支持这一概念，这些证据表明，对产蛋的投资被实验性地操纵。然而，有一个领域的知识，我们仍然只有一个非常初级的理解是关于因果机制(s)的潜在成本的繁殖。从历史上看，人们一直认为繁殖的成本依赖于能量或营养，它涉及一种相对简单的资源分配机制，在这种机制中，繁殖所需的资源从其他生理功能（例如免疫功能）中重新分配出来，而这些功能反过来又会产生负面影响。最近有人提出，繁殖成本可能是由繁殖本身或繁殖背后的调节（生理）机制引起的。该项目将研究与此相关的两个观点：a)与产蛋有关的贫血会降低女性的有氧或运动表现，b)繁殖会增加对氧化应激（“细胞损伤”）的敏感性，这将性与死亡联系起来。我们的方法是实验性的，整合了进化生物学、生态学和生理学。例如，我们将使用药物增加或降低产蛋鸟的贫血水平，然后直接测试对飞行性能，繁殖成功率和后代生长的影响。这个项目将提供关于生殖成本背后的因果机制的新颖、全面的数据。此外，尽管这项工作通过生理学方法的应用可能看起来深奥，但我们的工作将为有关环境变化（气候变化）对鸟类种群（例如地中海蓝山雀种群和北极筑巢的绒鸭）的影响的关键问题提供新的见解，包括保护和管理关注的物种（例如大理石纹小海豚）。

What prevents animals, including humans, from producing as many offspring of the highest quality as they like? Evolutionary biology provides the answer that there is a 'cost' to reproduction wherein the benefits of increased investment in a current reproductive bout are offset by costs in terms of current condition, future fecundity and survival. In birds, considerable evidence from studies where investment in egg production has been experimentally-manipulated supports this concept. However, one area of knowledge where we still have only a very rudimentary understanding is with regard to the causal mechanism(s) underlying costs of reproduction. Historically, it has been assumed that the cost of reproduction is energy or nutrient-dependent and that it involves a relatively simple resource-allocation mechanism where resources required for reproduction are reallocated away from other physiological functions (e.g. immune function) which in turn have negative effects. More recently it has been suggested that costs of reproduction might instead be caused by reproduction itself or the regulatory (physiological) mechanisms underlying reproduction. This project will investigate two ideas related to this: a) that anemia associated with egg production decreases the aerobic or exercise performance of females, and b) that reproduction increases susceptibility to oxidative stress ("cellular damage") and that this links sex and death. Our approach is experimental and integrates evolutionary biology, ecology and physiology. For example, we will use drugs to increase or decrease the level of anemia in laying birds and then directly test effects on flight performance, breeding success, and offspring growth. This project will provide novel, comprehensive data on causal mechanisms underlying costs of reproduction. Furthermore, although this work might seem esoteric through the application of physiological approaches our work will provide novel insight into key questions concerning effects of environmental variation (climate change) on avian populations (e.g. Mediterranean blue tit populations and Arctic-nesting eider ducks), including species of conservation and management concern (e.g. marbled murrelets).