Immune function versus reproduction: the mediation of life history trade-offs in a risky environment

资源是有限的，必须在身体的不同功能之间进行分配，换句话说，鱼与熊掌不可兼得。这导致了我们在许多不同物种中看到的权衡，例如，你可以有很多小婴儿或几个大婴儿，或者你可以迅速成熟，生下小个头的孩子，或者成长得慢一点，生下大个头的孩子。这些权衡为理解自然界中产生生物多样性的多种多样的生命史的进化提供了关键，因为不同的生物体对这一困境有不同的解决方案。一个这样的权衡是在维持你自己的健康和把精力投入生育之间；生物体可以选择将有限的资源用于后代或自身，但不能两者兼而有之。然而，在包括人类在内的少数生物中，这种选择尤为明显，因为人类参与了代价高昂的亲代照顾行为。大多数哺乳动物和鸟类，甚至一些无脊椎动物都投入时间和资源来喂养和保护它们的后代，而不是抛弃它们的后代。在这些生物中，大部分可用资源用于繁殖，留给自我维持的资源较少。我们观察到的解决方案是在当前环境中为每个物种提供最高适应度回报的进化结果。但是如果环境改变了会发生什么呢？随着寄生虫越来越多，气候变暖增加了疾病的风险。疾病是一种常见的威胁，可能会改变父母提供的护理量。他们可能需要花更多的精力来保持健康，因此忽视了他们的孩子，或者患病的父母可能会对他们的孩子付出额外的照顾，因为他们不太可能活下来生更多的孩子。研究表明，在多种动物物种中，关爱行为和对疾病的免疫反应都是由相同的激素控制的。在昆虫中，这些激素有相反的作用：增加照顾行为和降低免疫力。这意味着，通过研究健康和患病个体的关爱行为，同时控制他们的激素水平，我们可以揭示控制父母做出选择的机制。我将用埋葬甲虫来验证这些想法，因为这些昆虫几乎是独一无二的，因为它们的父母都为它们的后代准备食物、饲料和照顾。它们的关爱行为是有益的，因为被忽视的后代比接受关爱的后代生存的可能性更小，成长的速度也更慢。利用这个物种，我将展示患病父母的照顾选择是如何变化的，无论受感染的母亲还是父亲将照顾的成本转移到他们的伴侣身上，以及这些选择是如何由激素调节的。这将为如何控制权衡以及它们在高风险环境中如何变化提供重要的见解。

Resources are limited and must be divided between different functions in the body, in other words, you can't have your cake and eat it. This leads to trade-offs that we see in many different species, for example, you can have lots of small babies or few larger babies, or you can mature rapidly and have children at a small size, or grow more slowly and have children at a larger size. These trade-offs provide the key to understanding the evolution of the many and varied life-histories that generate biodiversity in the natural world, as different organisms derive different solutions to this dilemma. One such trade-off is that between maintaining your own health and putting energy into reproducing; organisms can choose to devote limited resources to their offspring or to themselves, but not both. However, this choice is particularly stark in the few organisms, including humans, who engage in costly parental care behaviours. Rather than abandoning their offspring to their fate, most mammals and birds, and even some invertebrates invest time and resources into feeding and protecting their offspring. In these organisms a large proportion of the available resources are devoted to reproduction, leaving fewer resources for self maintenance. The solution we observe is the evolutionary outcome that has been selected to provide the highest fitness returns for each species in the current environment. But what happens if the environment changes? Our warming climate is increasing the risk of disease as parasites become more abundant. Disease is a common threat that could change the amount of care that parents deliver. They may need to spend more effort on getting healthy and so neglect their children, or diseased parents may lavish extra care on their children because they are unlikely to survive to have more. Studies have shown that caring behaviours and immune responses to disease are both controlled by the same hormones in a variety of animal species. In insects, these hormones have opposite effects: increasing caring behaviour and decreasing immunity. This means that by studying caring behaviour in healthy and diseased individuals, whilst manipulating their hormone levels, we can uncover the mechanisms that control the choices parents make.I will test these ideas using burying beetles because these insects are almost unique in that both parents prepare food, feed and care for their offspring. Their caring behaviour is beneficial, as neglected offspring are less likely to survive and will grow less quickly than offspring that receive care. Using this species, I will demonstrate how caring choices change in diseased parents, whether infected mothers or fathers shift the costs of care onto their partners, and how these choices are mediated by hormones. This will provide important insights into how trade-offs are controlled and how they change in a high risk environment.