Identifying the genes that confer evolutionary adaptation to environmental temperature in an ectotherm

许多动物在寒冷的条件下长得更大。例如，温血动物，如鸟类和哺乳动物，在其地理范围较冷的地区往往体型较大。这种模式是有道理的，因为大型动物更容易保暖，因为它们有更大体积的发热组织，相对于身体表面的热量散失到环境中的面积来说。然而，很明显，冷血动物在寒冷中也会变大，这个项目的目的是找出原因。这是一个重要的话题，因为全球气候变化将使动物暴露在不断变化的温度下，我们需要了解它们将如何应对。鱼类等食用动物是冷血动物，我们的工作将直接关系到了解它们的生长效率如何受到温度的影响。为了做到这一点，我们将把重点放在一种小动物上，果蝇，它有广泛的地理分布。果蝇在高纬度地区进化得更大；不同种群的苍蝇在同一环境中生长的实验表明，它们的大小在基因上是不同的。温度似乎是高纬度地区更大体型进化的一个关键变量，因为在实验中，果蝇在实验室的不同温度下进化数年，在较低的培养温度下也会导致遗传上更大的体型。此外，来自同一种群的苍蝇在不同温度下长大成人，在较低温度下生长的成虫体型更大，这表明温度对体型有直接的环境影响。我们将发现在寒冷中体型变大的原因。首先，我们将确定在自然界中高纬度地区产生较大体型的基因。我们将通过绘制它们在遗传物质中的位置和寻找基因表达的改变模式来做到这一点。关键的是，我们将通过实验诱导我们认为至关重要的基因变异，并检查它们对体型的影响，从而证实我们的鉴定。我们将通过测量具有“热”和“冷”基因变异的果蝇在不同温度下的表现，来测试温度在体型进化中的重要性。我们还将发现哪些基因在不同温度下的生长过程中表现出不同的表达。通过识别控制体型随温度变化的基因和途径，我们将开始理解冷血动物在寒冷中变大的原因。

Many animals grow to be larger under cold conditions. For instance, warm-blooded animals such as species of birds and mammals often have larger body size in the colder parts of their geographical range. This pattern makes sense because it is easier for a large animal to keep warm, since it has a larger volume of heat-producing tissue in relation to the area of the body surface over which heat is lost to the environment. However, it has become apparent that cold-blooded creatures too become large in the cold, and the aim of this project is to find out why. This is an important topic, because global climate change will expose animals to changing temperature and we need to understand how they will respond. Food animals such as fish are cold-blooded and our work will be directly relevant to understanding how their growth efficiency is altered by temperature. To do this, we shall focus on a small animal, the fruit fly Drosophila, which has a wide geographic range. Fruit flies evolve to be larger at higher latitudes; experiments where flies from different populations are grown in the same environment shows that they differ genetically in size. Temperature seems to be a critical variable in the evolution of larger body size at higher latitudes, because experiments where flies are allowed to evolve for several years at different temperatures in the laboratory also result in genetically larger body size at lower culture temperatures. In addition, flies from the same population that grow up to adulthood at different temperatures produce larger adults with growth at lower temperatures, showing that there is a direct, environmental effect of temperature on size. We shall discover the reasons for larger size in the cold. First, we shall identify the genes that produce larger body size at higher latitudes in nature. We shall do this by mapping their location in the genetic material and by looking for altered patterns of gene expression. Critically, we shall then confirm our identification by experimentally inducing the genetic variants that we think are critical and checking their effects on body size. We shall test the importance of temperature in the evolution of body size, by measuring the performance of flies with the 'hot' and 'cold' genetic variants at different temperatures. We shall also find out which genes show altered expression during growth at different temperatures. By identifying the genes and pathways that control changes in body size in response to temperature, we shall start to understand the reasons why cold-blooded animals become larger in the cold.