The Additive Genetic Variance of Fitness in Semi-Natural and Laboratory Environments

适应性--个体产生后代的能力--是达尔文自然选择理论的核心概念。然而，如果健康没有遗传基础，那么健康的个体就不能将他们的优势传递给他们的后代，而自然选择的进化是不可能的。正因为如此，对于进化生物学家来说，适应性可遗传的程度是至关重要的。然而，衡量适合度的遗传决定论是非常困难的，因为传统上需要跟踪大量个人及其亲属，并记录他们的出生和死亡。因此，我们只对有限范围的物种进行了野外估计，所有这些物种都有相当大的不确定性。来自实验室的估计更为常见，但尚不清楚它们的相关性有多大，因为野生个体的适合度可能取决于它们对抗寄生虫、躲避捕食者和与竞争对手竞争的能力，而所有这些在实验室可能都不存在。使用数学和计算机模拟，我们已经证明，通过跟踪基因组中的所有基因并测量它们留下多少后代，也可以衡量适应性的遗传决定论。鉴于基因组测序成本的下降，这种替代方法有许多优点，目前是绝大多数无法单独追踪的物种的唯一可行解决方案。果蝇，黑腹果蝇，是世界上研究最深入的实验室生物之一，被广泛应用于进化生物学和其他领域。在这项资助中，我们的目标是测量在模拟野外条件下饲养的野生苍蝇的适合性的遗传决定论，为非脊椎动物提供第一个估计。我们还将在实验室条件下进行同样的实验，看看那些让更多后代留在实验室的基因是否与让更多后代留在野外的基因相同。如果是这样，那么在实验室中测量的适合度很可能是野外测量的一个很好的替代品，但如果涉及不同的基因，那么实验室研究可能在自然环境中几乎没有相关性。跟踪基因而不是个体的另一个好处是，我们可以看到哪些特征使成功的基因成功。是因为它们编码了一种更有用的蛋白质，还是因为它们在更大程度上或在更好的时间和地点部署了现有的蛋白质？成功的基因是否倾向于具有与免疫相关的功能？成功的基因更有可能位于X染色体上吗？这些问题，以及许多类似的问题，都是遗传学家反复提出的，他们试图通过观察基因组中留下的历史签名来间接回答这些问题。在这里，我们希望使用一种对基因位置和功能特别了解的有机体来实时解决这些类型的问题。

Fitness - the capacity of individuals to produce descendants - is the central concept of Darwin's theory of natural selection. However, if fitness does not have a genetic basis then fit individuals cannot transmit their superiority to their offspring, and evolution by natural selection is impossible. Because of this, the degree to which fitness is heritable is of central importance to evolutionary biologists. However, measuring the genetic determinism of fitness is very difficult because traditionally a large number of individuals and their relatives need to be tracked and their births and deaths recorded. Consequently, we only have estimates from the wild for a limited range of species, all of which come with considerable uncertainty. Estimates from the laboratory are more commonplace, but it is not clear how relevant they are since the fitnesses of wild individuals are probably dependent on how well they combat parasites, evade predators and compete with competitors, all of which may be absent in the laboratory.Using mathematics and computer simulations we have shown that the genetic determinism of fitness can also be measured by tracking all genes in the genome and measuring how many descendants they leave. Given the falling costs of genome sequencing this alternative method has many advantages, and is currently the only feasible solution for the vast majority of species which cannot be individually tracked. The fruit fly, Drosophila melanogaster, is one of the best studied laboratory organisms in the world and is extensively used in evolutionary biology and beyond. In this grant we aim to measure the genetic determinism of fitness in wild flies raised in conditions which simulate the wild, to provide the first estimate for a non-vertebrate animal. We will also perform the same experiment under laboratory conditions to see if those genes that leave more descendants in the laboratory are the same genes that leave more descendants in the wild. If this is the case, then fitness measured in the laboratory is probably a good surrogate for that in the wild, but if different genes are involved then laboratory studies may have little relevance in a natural context.An additional advantage of tracking genes rather than individuals is that we can see what features make successful genes successful. Is it because they encode for a more useful protein, or is it because they deploy an existing protein to a greater extent or at a better time and place? Do successful genes tend to have functions that relate to immunity? Are successful genes more likely to be located on the X chromosome? These questions, and many similar ones, have been repeatedly asked by geneticists who have sought to answer them indirectly, by looking at historical signatures left behind in genomes. Here, we hope to address these types of questions in real-time using an organism in which gene location and function are exceptionally well understood.