Testing hypotheses for the developmental basis of a morphological novelty in treehoppers

新结构的起源往往会促进物种的多样化。因此，理解新颖性是如何产生的是进化生物学中的一个关键问题。理解新颖性是如何产生的一种方法是比较具有新奇结构的物种的发展及其缺乏新奇结构的近亲。在节肢动物中，体壁的突起一直是包括昆虫翅膀在内的新结构的重复来源。这项研究采用比较的方法来确定一种新的体壁生长是如何产生的，也就是一群被称为树跳虫的真正昆虫的“头盔”。这种结构允许树跳虫采取各种各样的形状，例如通过模仿另一种有机体或通过伪装来提高存活率。该项目将通过向本科生提供研究经验来加强科学培训，包括那些从旨在加强科学界代表性不足的群体参与的方案中招募的本科生。它还将为研究生和博士后研究员提供培训。树跳虫也将被用作公开宣传昆虫多样性的工具。高度进化的树蝉(蜂科和近亲)前胸头盔是一个三维雕塑，假设是通过三个过程之一进化的：祖先体壁发育图案网络的精加工，翅膀图案网络的共选或腿部图案网络的共选。这些假说对不同组织类型和物种的基因表达和功能的相似性和差异性模式进行了具体预测。该项目将比较转录学与进化背景下的基因功能分析相结合，以检验这些预测。这项工作还将测试与分子定义的翼系列同系物在无翼前胸段发生相关的假说。这些项目目标将通过以下方式实现：(1)比较两种树蝉的组织和阶段特异性转录，包括新开发的发育模型Entylia carinata和两个无头盔的近亲；(2)利用前胸和中胸之间的同源转换来确定前胸头盔和中胸的序列同源部分；(3)使用反向遗传学和qPCR来分析与头盔发育有关的发育模式基因在隆起圆顶潜蝇和外群半翅目筋膜圆锥虫中的功能。

The origin of novel structures often fuels the diversification of species. Understanding how novelty arises is thus a key question in evolutionary biology. One approach to understanding how novelty arises is to compare development in species with the novel structure and their close relatives lacking it. In arthropods, outgrowths of the body wall have served as a repeated source of novel structures, including insect wings. This research takes a comparative approach to determine how a novel body wall outgrowth, the "helmet" of a group of true bugs called treehoppers, arose. This structure allows treehoppers to take on a wide diversity of shapes that may increase survival, for example by mimicking another organism or through camouflage. This project will enhance scientific training by providing research experience to undergraduates, including those recruited from programs designed to enhance the participation of groups underrepresented in science. It will also provide training to a graduate student and postdoctoral researcher. Treehoppers will also be used as a tool for public outreach about insect diversity. The highly evolvable prothoracic helmet of treehoppers (family Membracidae and close relatives) is a three-dimensional sculpture that is hypothesized to have evolved by one of three processes: elaboration of the ancestral body wall developmental patterning network, cooption of the wing patterning network or cooption of the leg patterning network. These hypotheses make specific predictions about patterns of similarity and difference in gene expression and function across tissue types and species. This project combines comparative transcriptomics with the analysis of gene function in an evolutionary context to test these predictions. This work will also test hypotheses related to the occurrence of molecularly-defined wing serial homologues in the wingless prothoracic segment. These project goals will be accomplished by (1) comparing tissue- and stage-specific transcriptomes of two treehoppers, including a newly developed developmental model Entylia carinata, and two helmet-less relatives; (2) using homeotic transformations between the prothorax and mesothorax to identify serially homologous parts of the pronotal helmet and mesothorax; (3) using reverse genetics and qPCR to analyze functions of developmental patterning genes involved in helmet development in both the treehopper E. carinata and an outgroup hemipteran, Oncopeltus fasciatus.