Genetic architecture and constraint in social evolution

虽然达尔文的“适者生存”的思想是我们理解这个星球上生命多样性的核心，但合作行为的进化和维持仍然是一个难题。这是因为，当合作的个体采取某种代价高昂的行动来帮助彼此时，他们就面临着破坏性作弊者的风险，这些作弊者不支付他们公平的成本份额。换句话说，如果欺骗是一种更好的策略，那么合作行为是如何在种群中维持的呢？为了更好地理解这一问题，我们认为，首先必须确定调控合作行为的基因和途径的性质。这是因为，尽管进化理论可能提出了最佳策略，但所需的遗传变化可能是不可能的。例如，某些策略可能不存在，因为任何收益都可能被其他适应度成本抵消。或者，它们调节行为的基因和途径可能是以这样一种方式组织的，进化根本不可能塑造它们实现最佳或有利的策略。在这项资助中，我们建议使用一个简单的系统来研究合作行为，即土壤中的社会阿米巴D。盘状突在有利条件下，D.盘状变形虫以单细胞个体存在，通过以细菌为食而生长和分裂。然而，在饥饿时，多达100，000个变形虫聚集并合作形成多细胞子实体，其由死柄细胞支持的哈代孢子组成。因此，茎细胞牺牲自己来帮助孢子的传播，这就提出了一个问题：为什么选择不会导致不支付茎生产成本公平份额的个体不受限制的欺骗。为了实现这一目标，我们将采用一种新的组合的方法在D。discoideum允许合作行为进行分析与强大的力量。我们最近发现，即使在少数不同的D。discoideum菌株，可以检测到不同的社会策略。在这个提案中描述的工作，将允许我们定义和分类的策略在一个更大的一组菌株的数量，因为这可以用来确定不同的“方式”进化允许社会策略被修改的数量。然后，我们将通过寻找具有改变的社会行为的突变株来询问这些是否对应于不同的分子或遗传途径。最后，我们将使用这些数据来生成模型，使我们能够更好地从理论上理解合作行为是如何维持的，进化结果是如何受到约束的。

Although the Darwinian idea of 'survival of the fittest' is central to our understanding of the diversity of life on this planet, the evolution and maintenance of cooperative behaviour remains a conundrum. This is because when cooperating individuals perform some sort of costly act to help one another, they run the risk of disruptive cheaters that do not pay their fair share of the cost. In other words, if cheating is a better strategy, how is cooperative behaviour maintained within populations? In order to better understand this problem, we believe that it will first be important to identify the nature of the genes and pathways that regulate cooperative behaviours. This is because, although evolutionary theory may suggest the best strategy, the genetic changes required may not be possible. For example, some strategies may not exist because any gains may be offset by other fitness costs. Alternatively, the genes and pathways that they regulate behaviour may be organised in such a way that it simply is not be possible for evolution to mould them achieve the optimal or favoured strategy. In this grant, we propose to address each of these problems using a simple system for the study of cooperative behaviour, the soil dwelling social amoeba D. discoideum. Under favourable conditions, D. discoideum amoebae exist as single celled individuals that grow and divide by feeding on bacteria. Upon starvation, however, up to 100,000 amoebae aggregate and cooperate to make a multicellular fruiting body consisting of hardy spores supported by dead stalk cells. Stalk cells thus sacrifice themselves to help the dispersal of spores, raising the question of why selection does not lead to unchecked cheating by individuals that do not pay their fair share of the cost of stalk production. To achieve this goal, we will employ a novel combination of approaches in D. discoideum that allow cooperative behaviour to be analysed with great power. We have recently found that even within a small number different D. discoideum strains, different social strategies could be detected. The work described in this proposal, will allow us to define and classify the number of the strategies within a larger set of strains, because this can be used to determine the number of different 'ways' evolution has allowed social strategies to be modified. We will then ask whether these correspond to distinct molecular or genetic pathways by searching for mutant strains with altered social behaviour. Finally, we will use these data to generate models that will allow us to develop a better theoretical understanding of how cooperative behaviour is maintained and evolutionary outcomes constrained.