| Abstract |
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. |
