A Higher Level Classification of All Living Organisms

April A Higher Level Classification of All Living Organisms Michael A. Ruggiero 0 1 2 3 Dennis P. Gordon 0 1 2 3 Thomas M. Orrell 0 1 2 3 Nicolas Bailly 0 1 2 3 Thierry Bourgoin 0 1 2 3 Richard C. Brusca 0 1 2 3 Thomas Cavalier-Smith 0 1 2 3 Michael D. Guiry 0 1 2 3 Paul M. Kirk 0 1 2 3 0 1 Integrated Taxonomic Information System , National Museum of Natural History , Smithsonian Institution, Washington, District of Columbia, United States of America, 2 National Institute of Water & Atmospheric Research , Wellington , New Zealand, 3 WorldFish-FIN, Los Banos, Philippines, 4 Institut Systematique, Evolution, Biodiversite (ISYEB) , UMR 7205 MNHN-CNRS-UPMC-EPHE, Sorbonne Universites, Museum National d'Histoire Naturelle , 57, rue Cuvier, CP 50, F-75005, Paris , France , 5 Department of Ecology & Evolutionary Biology, University of Arizona, Tucson, Arizona, United States of America, 6 Department of Zoology, University of Oxford , Oxford , United Kingdom , 7 The AlgaeBase Foundation & Irish Seaweed Research Group, Ryan Institute, National University of Ireland , Galway, Ireland, 8 Mycology Section, Royal Botanic Gardens, Kew, London , United Kingdom 1 Received: July 8 , 2014 2 Academic Editor: Erik V. Thuesen, The Evergreen State College, UNITED STATES 3 A Higher Level Classification of All Living Organisms We present a consensus classification of life to embrace the more than 1.6 million species already provided by more than 3,000 taxonomists' expert opinions in a unified and coherent, hierarchically ranked system known as the Catalogue of Life (CoL). The intent of this collaborative effort is to provide a hierarchical classification serving not only the needs of the CoL's database providers but also the diverse public-domain user community, most of whom are familiar with the Linnaean conceptual system of ordering taxon relationships. This classification is neither phylogenetic nor evolutionary but instead represents a consensus view that accommodates taxonomic choices and practical compromises among diverse expert opinions, public usages, and conflicting evidence about the boundaries between taxa and the ranks of major taxa, including kingdoms. Certain key issues, some not fully resolved, are addressed in particular. Beyond its immediate use as a management tool for the CoL and ITIS (Integrated Taxonomic Information System), it is immediately valuable as a reference for taxonomic and biodiversity research, as a tool for societal communication, and as a classificatory backbone for biodiversity databases, museum collections, libraries, and textbooks. Such a modern comprehensive hierarchy has not previously existed at this level of specificity. - Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Competing Interests: The authors have declared that no competing interests exist. Biological classification (taxonomy) aims to simplify and order the immense diversity of life into coherent units called taxa that have widely accepted names and whose members share important properties. It synthesizes information concerning a great variety of characters (e.g., morphological; molecular: genes, metagenome, and metabolome; etho-ecological). There is currently no consensus among the world's taxonomists concerning which classification scheme to use for the overall hierarchy of life, in part because of the confusion resulting from Hennig's [1] redefinition of previous terminology of classification, which has not been universally accepted; the separate goals of cladification and classification [2]; and conflicting or unresolved evidence for phylogenetic relationships. The continuing advances in the use of specialized analytical tools from many different fields and their resulting conclusions and assumptions require regular updates as advances in knowledge are made. Biological classification can integrate diverse, character-based data in a phylogenetic framework, which allows a broad user community to utilize the disparate knowledge of shared biological properties of taxa. Phylogeny is, therefore, the basis for these biological classifications but there is still strong debate over their accounting for evolutionary divergence or information content other than the branching pattern [3]. Accordingly, classifications have often been labeled either phylogenetic or evolutionary, depending mainly upon whether or not they reject paraphyletic groups [3, 4]. While the type of classification to be used to support further exploration and analysis of any biological scenario may be important, it is not the subject of this paper. The proposed classification does not address detailed phylogenetic questions and, while hierarchical and reflective of phylogeny, is not itself a phylogenetic tree. The aim of this classification is to be a pragmatic means of managing the ever-increasing knowledge of the diversity of life, its relationships, characteristics, and properties. Indeed, the past two decades have witnessed an explosion in biodiversity research and informatics, emphasizing the need for a quality list of accepted scientific names of the more than 1.9 million described living species [5] and for greater consensus on how to classify them at higher taxonomic ranks. Since 2001, Species 2000 and the Integrated Taxonomic Information System (ITIS) have worked with their respective contributors to complete a comprehensive species list, called the Catalogue of Life (CoL). The CoL Annual Checklist (http://www.catalogueoflife.org/annual-checklist/2014/) already contains more than 1.6 million valid or accepted species names provided by more than 140 taxonomic databases involving more than 3,000 taxonomists [6]. More than 82% of the global species databases are provided at the rank of class or below (includes 1.3 million species), and more than 63% are provided at the rank of order or below (includes 1.0 million species). Owing to the heterogeneity in higher level classification among the contributed databases, the CoL managers sought a practical and coherent hierarchical classification that could serve as a framework for data integration. Here we explain the rationale behind the consensus higher level classification that we propose for CoL use. Our goal, therefore, is to provide a hierarchical classification for the CoL and its contributors that (a) is ranked to encompass ordinal-level taxa to facilitate a seamless import of contributing databases; (b) serves the needs of the diverse public-domain user community, most of whom are familiar with the Linnaean conceptual system of ordering taxon relationships; and (c) is likely to be more or less stable for the next five years. Such a modern comprehensive hierarchy did not previously exist at this level of specificity. In this sense it summarizes overarching aspects of the tree of life, including both paraphyletic and monophyletic groups, both being important in facilitating meaningful communication among scie (...truncated)