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

University Of Connecticut, Storrs CT

Investigators

Abstract

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.