This project aims to resolve the liverwort Tree Of Life. There is mounting evidence that liverworts (Phylum Marchantiophyta) were the first green plants to diversify on land some 500,000 million years ago and as such they are the oldest living lineage of terrestrial organisms. This species-rich group of small green plants is remarkably diverse in structure, and includes extremely ancient relictual lineages as well as more recent radiations of closely related species. The antiquity of liverworts and the rich biodiversity at all taxonomic levels provide an unparalleled window into early land plant diversification. This collaborative effort brings together experts from around the world for a multidisciplinary, highly integrated approach that combines anatomical and developmental features with DNA sequence and genome structural characters to resolve phylogenetic relationships across the entire spectrum of liverwort diversity. Three general types of data will be compiled: 1) conservative morphological and genome characters to resolve deep "backbone" relationships, 2) anatomical/developmental data to resolve intermediate-depth lineages, and 3) morphological and DNA sequence characters to resolve relationships among a sample of 800 taxa representing all genera of liverworts. A second major goal of the project is to integrate phylogenetic inferences and bionformatic efforts between this and other on-going NSF-supported projects, including several funded ATOL programs. These integrative activities include contributions to studies of genome structure and evolution across land plants, expansions of novel informatic tools to make methods, results, and implications widely accessible, and continued development of DNA sequence utilities that will benefit a broad range of scientists working on diverse organisms. This project relies on the cooperation with and integration among research programs focused on resolving the green plant Tree Of Life. Integrative activities are substantive and consequential, and include expansions to phylogenetic databases and methodological/conceptual aspects of work toward resolving the Tree Of Life. At least six post-doctoral associates and as many graduate students will be supported by the project, with substantial involvement of undergraduates as well. An effort to involve and retain individuals from underrepresented groups will be orchestrated through established federal programs that focus on such initiatives, including the Louis Stokes Alliance for Minority Participation and the McNair Scholars Program. A solid mentoring infrastructure will be developed within each research team to provide support and professional experiences that ensure productivity and success of all participants. Outreach efforts include web presentations on the morphology and identification of liverworts for educators at all levels, development of web-based materials and a workshop targeting secondary school teachers, and increasing public awareness through weekend field excursions.