The complexity of organisms is the product of genes, environmental conditions, and developmental processes. These interactions are central themes in many biological and medical disciplines, and occupy a particularly prominent position in evolutionary biology. Ultimately, all evolutionary diversification of organismal form and function is only possible through changes in the nature of at least some of these interactions. The research project will explore the degree, nature and consequences of these interactions in the origin, development, and diversification of a complex class of traits that is emerging as a new model system in integrative organismal biology: beetle horns. Horned beetles offer incredible organismal richness and diversity, as well as accessibility to experimental manipulation. Using genetic, molecular, and biochemical approaches this research project will 1) determine which genes underlie the formation of horns, 2) explore which genes allow horn development to be more or less responsive to nutritional conditions, and 3) explore how genes and hormones interact during horn development and evolution. This research will not only make a novel contribution to the fields of development, physiology, and evolution, but also facilitate an integration of the evolution of developmental processes with the behavioral and ecological mechanisms that guide such evolution in nature. This research program also interfaces tightly with several educational and outreach efforts. Firstly, six high school teachers and three minority high school students will be recruited into the investigators' laboratories during the summer to immerse them in research in development, evolution, and ecology. Teachers and students will be recruited through existing outreach programs with which both investigators are already affiliated. Secondly, this project will help train at least seven young scientists (6 undergraduate students, 1 postdoc) in intensive interdisciplinary research integrating developmental biology, physiology, genetics, molecular biology and evolution. Lastly, results from the proposed research will contribute to course curricula and will be used as exemplars in two graduate courses on Evolution and Development, and Developmental Plasticity and Evolution.
The development and evolution of all organisms is shaped by the interactions between genes and environmental conditions, which is further constrained by the nature of developmental processes. These interdependencies determine the range and types of organismal variation that development can produce, the robustness of development to stress, and the capacity of developmental processes to initiate the origin of novel variants or traits. This project focused on the roles of genes, environmental conditions (mostly nutrition), and the genetic and hormonal regulation of insect development in the development and diversification of complex traits. Specifically, it focused on a group of insects famous for their extraordinary diversity and nutritional responsiveness during development - horned beetles. This research aimed to identify (a) which genes and developmental processes are needed to develop diverse morphological traits; (b) how nutritional and hormonal factors influence the development of these traits; and (c) how changes in the conversation between genes, nutrition, and hormones allow these traits to alter their environmental responsiveness, for instance as a function of body region, or gender, or species. This research is among the first to characterize the complexity of factors that contribute to variation in gene expression. It illustrates, for instance, that traits can differ dramatically in the diversity of genes that respond to nutritional stress, even though these traits may be developing side by side in the same individual. Similarly, this research shows that the "same" trait in males and females may differ by orders of magnitude in the diversity of genes whose expression is affected by nutritional stress. In addition, this research has identified and experimentally analyzed key developmental pathways that serve as points of integration for developmental information, enabling developing structures to "know" whether they are growing in a male or female, what their exact location is, and whether to adjust their final size due to nutrient limitations. Lastly, this research project helped train at least 10 young scientists (8 undergraduate students, 1 graduate student, 1 postdoc), and in collaboration with a local children's museum for science, health and technology provided training and educational resources in insect biology and beyond to approximately 200 local and regional K- 12 teachers, an effort that has lastingly enriched K-12 science education in South-Central Indiana.
