Abstract
Because many animal species are undescribed, and because the identification of known species is often difficult, interim taxonomic nomenclature has often been used in biodiversity analysis. By assigning individuals to presumptive species, called operational taxonomic units (OTUs), these systems speed investigations into the patterning of biodiversity and enable studies that would otherwise be impossible. Although OTUs have conventionally been separated through their morphological divergence, DNA-based delineations are not only feasible, but have important advantages. OTU designation can be automated, data can be readily archived, and results can be easily compared among investigations. This study exploits these attributes to develop a persistent, species-level taxonomic registry for the animal kingdom based on the analysis of patterns of nucleotide variation in the barcode region of the cytochrome c oxidase I (COI) gene. It begins by examining the correspondence between groups of specimens identified to a species through prior taxonomic work and those inferred from the analysis of COI sequence variation using one new (RESL) and four established (ABGD, CROP, GMYC, jMOTU) algorithms. It subsequently describes the implementation, and structural attributes of the Barcode Index Number (BIN) system. Aside from a pragmatic role in biodiversity assessments, BINs will aid revisionary taxonomy by flagging possible cases of synonymy, and by collating geographical information, descriptive metadata, and images for specimens that are likely to belong to the same species, even if it is undescribed. More than 274,000 BIN web pages are now available, creating a biodiversity resource that is positioned for rapid growth.
Highlights
Most animal species await description [1] and many named taxa represent a species complex [2]
This paper describes the establishment of the Barcode Index Number (BIN) system as a persistent registry for animal operational taxonomic units (OTUs) recognized through sequence variation in the c oxidase I (COI) DNA barcode region
Its development had two primary motivations – to enable evaluations of biodiversity patterns in advance of fully developed taxonomy and to aid taxonomic progress. It builds on prior studies which have established that most animal species show less than 2% intraspecific variation at COI, but more than 4% divergence from their nearest neighbour [13,56]
Summary
Most animal species await description [1] and many named taxa represent a species complex [2]. It has been estimated that the cost of describing all animal species will exceed US$270 billion and require centuries [3,4]. Given this situation, it is clear that new approaches are needed to support biodiversity assessments in advance of fully developed species-level taxonomy. Biodiversity researchers have often attempted to address the taxonomic impediment in a local or regional context by assigning specimens to operational taxonomic units (OTUs) using morphological differences perceived to be indicators of species boundaries. It is very difficult to codify morphology-based OTUs in a format which allows their comparison among studies. The adoption of DNA sequences as a basis for OTU classification escapes this constraint; their digital nature aids the application of standardized protocols for OTU designation, the comparison of results among studies, and data preservation
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