Evolution, genetic basis and behavioural consequences of cuticular hydrocarbon diversification: the case of parabiotic ants

昆虫表皮上覆盖着表皮碳氢化合物（CHC）。它们有两个重要的功能：作为干燥屏障和化学通讯。特别是在社会性昆虫中，CHC配置文件编码了大量的信息，如物种成员，性别，生殖种姓和殖民地成员。尽管他们的高度重要性，然而，CHC档案的演变和潜在的遗传机制知之甚少。此外，鲜为人知的是，CHC是重要的种内和种间recognition.We建议调查一个模型系统，这是非常适合解决这些问题。新热带区的Crematogaster levior和Camponotus femoratus是共生关系，即它们以互惠的方式共享一个共同的巢穴。它们的CHC谱异常多样：在这两个分类群中，存在多种化学型，其中很少或没有共同的化合物。相比之下，大多数其他物种的CHC变异仅限于相同化合物的数量变异。因此，我们的模型系统显示了密切相关的个体之间的高化学变异性，这些个体可能在生理学和生态学上相似。这种独特的组合开辟了有趣的机会，研究表皮碳氢化合物的演变，化学多样化的原因和后果及其对物种形成的作用。我们将研究CHC多样性的遗传基础以及化学分化在种内和种间交流中的作用。首先，我们将研究Cr种群间的遗传和化学分化。在法属圭亚那，并阐明人口结构，通过测序（GBS）基因分型。这将使我们能够调查遗传，化学和地理距离的关系，以揭示化学分化的生殖隔离和物种形成的作用。其次，我们将研究化学分化如何影响巢识别和识别相关的物种。使用CHC组分的行为测定，我们将研究哪些CHC类别与种内和种间的灭绝有关。levior和Ca. femoratus，我们将研究哪些基因在不同的化学型中差异表达和/或差异选择。我们的研究结果将为CHC分化的遗传调控提供新的见解，这在很大程度上仍然是未知的。为了验证已识别候选基因座的功能，我们将通过RNAi使它们沉默，并确定对CHC谱的影响。CHC变化对巢友和物种识别的生物相关性将在侵略生物测定中确定。化学型之间的高CHC变化表明，DNA和/或调控水平的小变化足以诱导CHC谱的大规模变化。我们的项目将提供许多新的见解的进化，遗传机制和行为后果的表皮碳氢化合物多样化的蚂蚁。

Insect cuticles are covered with cuticular hydrocarbons (CHC). They serve two important functions: as desiccation barrier and for chemical communication. Especially in social insects, CHC profiles encode a multitude of information such as species membership, sex, reproductive caste, and colony membership. Despite their high importance, however, the evolution of CHC profiles and the underlying genetic mechanisms are little understood. Also, little is known which CHC are important for intra- and interspecific recognition.We propose to investigate a model system which is highly suited for addressing such questions. The neotropical ants Crematogaster levior and Camponotus femoratus are parabiotically associated, i.e. they share a common nest in a mutualistic way. Their CHC profiles are unusually diverse: in both taxa, multiple chemotypes exist, which have few or no compounds in common. In contrast, CHC variation in most other species is restricted to quantitative variation of the same compounds. Thus, our model system shows high chemical variability between closely related individuals, which are likely to be physiologically and ecologically similar. This unique combination opens up intriguing opportunities to investigate the evolution of cuticular hydrocarbon profiles, the causes and consequences of chemical diversification and its role for speciation. We will study the genetic basis of CHC diversity as well as the role of chemical differentiation for intra- and interspecific communication.First, we will study genetic and chemical differentiation across populations of Cr. levior in French Guiana, and elucidate population structure using genotyping by sequencing (GBS). This will allow us to investigate the relations of genetic, chemical and geographic distance to reveal the role of chemical differentiation for reproductive isolation and speciation. Second, we will study how chemical differentiation affects nestmate recognition and recognition by an associated species. Using behavioural assays with CHC fractions, we will study which CHC classes are relevant for intra- and interspecific recognition.For both Cr. levior and Ca. femoratus, we will investigate which genes are differentially expressed and/or differentially selected in different chemotypes. Our results will provide novel insights into the genetic regulation of CHC differentiation, which is still largely unknown. To verify the functionality of identified candidate loci, we will silence them via RNAi and determine the effect on CHC profiles. The biological relevance of CHC changes for nestmate and species recognition will be determined in aggression bioassays. The high CHC variation between chemotypes suggests that small changes on DNA and/or regulatory level suffice to induce large-scale changes in the CHC profile. Our project will provide a multitude of novel insights on the evolution, genetic mechanisms and behavioural consequences of cuticular hydrocarbon diversification in ants.