CAREER: Identifying controls on size evolution through comparative analysis

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CAREER: Identifying controls on size evolution through comparative analysisJonathan L. Payne, Department of Geological and Environmental Sciences, Stanford UniversityEAR-1151022ABSTRACTSize and function are inseparable in biology because a wide variety of physiological and life-history traits scale with size. Patterns of size evolution can therefore complement taxonomic diversity and geochemical proxy data by providing quantitative constraints on the influence of ecological interactions and environmental change on major events in the history of life, from the origin of eukaryotes to the Cambrian explosion, the early Paleozoic radiation of marine animals, the Cenozoic rise of mammals, the circumstances of mass extinctions and subsequent recoveries, responses to climate change, and potential influences of sampling bias on taxonomic diversity. One of the most intriguing observations in the study of size evolution is that patterns of change are often shared across distantly related taxa during intervals of taxonomic radiation, mass extinction, and global environmental change. Just as comprehensive, global compilation of stratigraphic ranges has enabled vast advances in our understanding of biodiversity dynamics, an analogous compilation of body sizes spanning the Phanerozic is critical for identifying controls on the evolution of this key functional trait. The goal of this study is to determine if and when evolutionary dynamics have been shared across major clades through the Phanerozoic and thereby identify the factors that shape the evolution of organism size. To accomplish this goal, PI will compile comprehensive, genus-level size datasets for foraminifera, brachiopods, and gastropods. These groups comprise more than 25% of the genus diversity in the marine fossil record but differ in basic anatomy, physiology, and ecology. By identifying the best model for size evolution within each clade, determining whether or not the mode of size evolution has shifted during the Phanerozoic, and testing whether evolutionary dynamics are shared across these groups, PI will determine whether there are universal ecological or environmental controls on size evolution or if, instead, the dynamics of size evolution vary among groups as a function of ecological and physiological properties or change through geological time as a function of biological or environmental circumstances.This study will provide the foundation for PI's long-term education and outreach program. Participation in the collection and analysis of body size data requires relatively little technical training or access to expensive instruments or facilities. Consequently, it offers an ideal opportunity to involve students at all levels directly in data collection and analysis, both in the classroom and as part of intensive summer research programs. Each summer, six high school students and one high school teacher will assist undergraduates and the graduate student in data collection and preliminary analyses. The high school teacher will continue data collection and analysis during the academic year at Yerba Buena High School, a school that serves a majority population of economically disadvantaged families and underrepresented groups in STEM fields. The graduate student will visit the class on a biweekly basis to supervise data collection and analysis, and the class will visit Stanford each spring as a capstone experience. The PI will develop a new freshman seminar class with exercises based on data from this project. Project success will be evaluated using surveys to assess student attitudes toward STEM fields and future plans before and after participation in the project, as well as long-term tracking of students' educational histories in future years.Data collected from this project will be archived as stand-alone datasets at Dryad, but will also be entered into the Paleobiology Database, an open-access, community-wide compilation of fossil occurrence data. Size data are integral to analyses of evolutionary dynamics and the fidelity of the fossil record. Because the data produced in this study will cover a significant fraction of known marine genera, they are likely to be used broadly by the community in studies unrelated to the proposed project.