Costs and consequences of the structured family

结构化家庭的成本和后果

• 批准号: NE/E001351/1
• 负责人: Nicholas Royle
• 金额: $ 10.74万
• 依托单位: UNIVERSITY OF EXETER
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FE001351%2F1
• 关键词: Costs; consequences; structured; family; Costs; consequences; structured; family

The environment experienced during early life can have profound effects on health and fitness as adults. In species that provide parental care dependent young are often reared together in broods. Close relations consequently provide the social environment in which growth and development takes place. However, parental care is costly and parents often initially 'overproduce' the amount of offspring they can, or are willing to, rear. Consequently offspring demand may often exceed parental supply of resources, such as food, which are necessary for growth and development of young. This creates the conditions for conflicts of interest over the supply of parental investment amongst family members. The amount of resources provided by parents is ultimately dependent upon the availability of resources in the environment. In many birds resource availability during breeding is often unpredictable, and parents may not have full control over the distribution of food among offspring. However, parents can simultaneously track resources in the environment and increase control over within-brood food allocation via maternal effects. Asynchronous hatching, as a consequence of early onset of incubation, is one such maternal effect that leads to the creation of different castes of progeny. First hatched 'core' chicks enjoy substantial fitness advantages over last hatched 'marginal' chicks. Core brood chicks are largely buffered from environmental and developmental uncertainty by marginal chicks, such that the development and fitness of core chicks is largely independent of the number of marginal chicks within a brood. In contrast the fitness prospects of marginal offspring are strongly dependent upon both the core brood size and environmental conditions. The creation of such a 'structured family' through phenotypic handicapping of some offspring ensures parents can more easily tailor brood size to match current conditions and provides insurance against failure of core brood chicks. However, very little is known about the mechanisms utilised by marginal offspring to overcome the handicaps imposed by hatching asynchrony should conditions improve (for example if a core chick dies). In particular, the role of the quality of food available has not been examined. Increased availability of dietary antioxidants for example, such as carotenoids and vitamin E, have been shown to enhance growth, reduce susceptibility to pathogens and increase the ability of chicks to withstand oxidative stress. Evidence suggests that natural selection should favour compensatory resource allocation and growth if poor conditions experienced during early development subsequently improve. However, growth compensation is not free from costs, and it has recently been shown that costs of oxidative stress associated with rapid growth can be reduced by sufficient availability of antioxidants. Consequently the provision of antioxidants may be an important determinant of the ability of marginal chicks to respond to a change in food availability and compensate for a poor start in life. Different selection pressures in relation to sex as adults can also impose differential compensatory responses on males and females to a change in food availability. However, the importance of the quality of food available on the costs and consequences of the structured family has not previously been considered. This project will quantify the effects of compensatory resource allocation in relation to sex and family structure, and examine the cost basis of growth through the manipulation of antioxidant availability and subsequent measurement of oxidative stress in red-winged blackbirds (Agelaius phoeniceus). By focusing on marginal chicks, and their ability to respond to changes in their (social) environment through compensatory resource allocation this work will highlight key selection pressures and will assess plasticity of responses to changes in environmental conditions.

早年经历的环境可能会对成年人的健康和健康产生深远的影响。在提供依赖父母护理的物种中，幼年通常会养育在一起。因此，亲密关系提供了增长和发展的社会环境。但是，父母的护理成本很高，父母通常通常会“过度生产”他们可以或愿意养育的后代数量。因此，后代需求通常可能超过父母的资源供应，例如食物，这对于年轻人的增长和发展是必需的。这为家庭成员之间的父母投资供应而产生了利益冲突的条件。父母提供的资源数量最终取决于环境中资源的可用性。在许多鸟类中，繁殖过程中的资源可用性通常是不可预测的，父母可能无法完全控制食物在后代之间的分布。但是，父母可以同时跟踪环境中的资源，并通过母体效应来增加对育内食品内部分配的控制。由于孵化的早期发作，异步孵化是一种产妇的作用，从而导致产生不同的后代种姓。首先孵化的“核心”小鸡比最后孵化的“边缘”小鸡具有很大的健身优势。核心雏鸡在很大程度上是由于边缘小鸡的环境和发育不确定性所缓冲，因此核心小鸡的发育和适应性在很大程度上独立于育雏中的边际小鸡的数量。相比之下，边缘后代的适应性前景很大程度上取决于核心的育雏尺寸和环境条件。通过表型的某些后代的表型障碍，创建了这样的“结构化家庭”，确保父母更容易量身定制育雏量以匹配当前状况，并为核心育雏小鸡的失败提供保险。但是，对于边缘后代使用的机制来克服通过孵化异步施加的障碍的机制知之甚少（例如，如果核心小鸡死亡）。特别是，尚未检查可用食物质量的作用。例如，饮食中抗氧化剂的可用性增加，例如类胡萝卜素和维生素E，已显示可增强生长，降低对病原体的敏感性并提高雏鸡承受氧化应激的能力。有证据表明，如果早期发展期间经历的差状况不佳，自然选择应有利于补偿性资源分配和增长。但是，增长补偿并非没有成本，并且最近已证明，通过足够的抗氧化剂可用性可以降低与快速生长相关的氧化应激成本。因此，提供抗氧化剂可能是边际小鸡应对食物可用性变化并弥补生活差的差的重要决定因素。与性别有关的不同选择压力也可以对男性和女性对食物可用性的变化施加差异性补偿性反应。但是，以前尚未考虑食品质量对结构化家族的成本和后果的重要性。该项目将量化与性别和家庭结构相关的补偿性资源分配的影响，并通过操纵抗氧化剂的可用性以及随后在红翅黑鸟（Agelaius Phoeniceus）中测量氧化应激的成本基础。通过关注边际小鸡，以及通过补偿资源分配来应对（社会）环境变化的能力，这项工作将突出关键选择压力，并将评估对环境条件变化的反应的可塑性。