Biophysical and functional consequences of cuticular hydrocarbon variation in ants

角质碳氢化合物(CHC)几乎覆盖所有昆虫的身体。它们的组成是高度可变的：种内(例如驯化)变化涉及相同碳氢化合物的数量变化，而不同物种可能拥有完全不同的碳氢化合物。CHC层防止干燥，抵御病原体，并作为通讯信号。虽然CHC变异在沟通中的作用正在被深入研究，但人们对它如何影响防水和抵御病原体的能力知之甚少。这两种功能在很大程度上是由碳氢分子之间的相互作用决定的，这会影响CHC层的相行为、熔化行为和粘度。我们仍然很难知道CHC变异如何决定这些生理特征，以及它们如何影响CHC功能。在这里，我建议研究CHC变异如何影响蚂蚁的物理CHC特征以及防水和抵御真菌病原体的能力。首先，我将研究两个蚂蚁物种的种内差异：大陆和海洋种群之间适应CHC变化的程度(反应标准)。在驯化过程中，昆虫会改变它们的CHC特征，以增强抗旱性。由于受到更强烈的波动的影响，大陆种群应该比海洋种群进化出更大的反应标准，从而更好地应对波动。这两个物种的群体将沿着整个欧洲的海洋-大陆梯度收集，并在不同的温度条件下驯化。随后，我们将研究CHC在生物物理性质、干旱存活率、透水性和CHC诱导的真菌病原菌生长抑制方面的变化和驯化相关的变化。他们将在不同的政权之间进行比较，但也会在不同的人口之间进行比较。其次，我将研究物种间的差异，重点是昆虫物种之间最显著的CHC差异：它们是由不饱和碳氢化合物还是由多支链烷烃主导的。这种区别解释了种间CHC变异的主要原因，而几乎所有昆虫都有正构烷烃。我们将从物理特性、防水能力和对真菌生长的抑制等方面对这两种剖面类型的物种进行比较。特别是，我们将研究这些特性如何依赖于当前的温度，以及它们如何随着适应性CHC的变化而变化。综上所述，该项目将把化学成分与CHC层的物理表型和功能联系起来。尤其是CHC组成(不包括正构烷烃)和物理特性之间的联系是新的，以前几乎没有人研究过。它将揭示哪些化学和物理性状处于生物选择之下，从而有助于我们理解CHC的进化。此外，我们将能够评估物种和同种种群如何应对不同的气候。这将是预测他们如何应对气候变化的关键。

Cuticular hydrocarbons (CHCs) cover the body of nearly all insects. Their composition is highly variable: intraspecific (e.g. acclimatory) variation concerns quantitative changes of the same hydrocarbons, whereas different species can possess entirely different hydrocarbons. The CHC layer protects against desiccation, against pathogens, and serves as communication signal. While the role of CHC variation for communication is being intensively studied, considerably less is known about how it affects waterproofing and the ability to fend off pathogens. Both functions are largely determined by interactions between hydrocarbon molecules, which affect phase behaviour, melting behaviour, and viscosity of the CHC layer. We still hardly know how CHC variation determines these physical traits, and how they affect CHC functionality. Here, I propose to study how CHC variation affects physical CHC traits and the ability to waterproof and protect against fungal pathogens, in ants. Firstly, I will study intraspecific variation in two ant species: the extent of acclimatory CHC changes (the reaction norm) among continental and maritime populations. During acclimation, insects change their CHC profiles to enhance drought resistance. Being exposed to stronger fluctuations, continental populations should have evolved a larger reaction norm and thus a better ability to cope with fluctuations, than maritime ones. Colonies of both species will be collected along a maritime-continental gradient across Europe and acclimated at different temperature regimes. Subsequently, we will investigate CHC changes and acclimation-related changes in biophysical properties, drought survival, water permeability and CHC-induced growth inhibition of fungal pathogens. They will be compared across regimes, but also across populations. Secondly I will study interspecific variation, focusing on the most prominent CHC difference among insect species: whether they are dominated by unsaturated hydrocarbons or by multiply branched alkanes. This distinction explains a major part of interspecific CHC variation, whereas nearly all insects have n-alkanes. We will compare species of the two profile types concerning physical traits, waterproofing ability and the inhibition of fungal growth. In particular, we will investigate how these traits depend on the current temperature and how they change along with acclimatory CHC changes. Taken together, this project will link chemical composition to the physical phenotype and functionality of CHC layers. Especially the link between CHC composition (beyond n-alkanes) and physical traits is novel and has hardly been studied before. It will reveal which chemical and physical traits are under biological selection, and hence contribute to our understanding of CHC evolution. Moreover, we will be able to assess how species and conspecific populations can deal with different climates. This will be crucial to predict how they respond to climate change.