Abstract
DNA barcoding of aquatic macroinvertebrates holds much promise as a tool for taxonomic research and for providing the reliable identifications needed for water quality assessment programs. A prerequisite for identification using barcodes is a reliable reference library. We gathered 4165 sequences from the barcode region of the mitochondrial cytochrome c oxidase subunit I gene representing 264 nominal and 90 provisional species of mayflies (Insecta: Ephemeroptera) from Canada, Mexico, and the United States. No species shared barcode sequences and all can be identified with barcodes with the possible exception of some Caenis. Minimum interspecific distances ranged from 0.3–24.7% (mean: 12.5%), while the average intraspecific divergence was 1.97%. The latter value was inflated by the presence of very high divergences in some taxa. In fact, nearly 20% of the species included two or three haplotype clusters showing greater than 5.0% sequence divergence and some values are as high as 26.7%. Many of the species with high divergences are polyphyletic and likely represent species complexes. Indeed, many of these polyphyletic species have numerous synonyms and individuals in some barcode clusters show morphological attributes characteristic of the synonymized species. In light of our findings, it is imperative that type or topotype specimens be sequenced to correctly associate barcode clusters with morphological species concepts and to determine the status of currently synonymized species.
Highlights
DNA barcoding [1] of animals, the analysis of a standardized segment of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene, has rapidly become an important tool for the identification, delimitation, and discovery of species [1,2,3]
As much as 55% of the North American fauna may have coverage, and perhaps as much as 60% of the 583 species known from Canada and the United States
This paper presents the largest barcoding dataset of any order of aquatic insects, providing records for more than 4000 individuals from over 350 species. The analysis of both larvae and adults from several localities and some topotypes enabled identification with less ambiguity than in the past. This allowed the correction of previously misidentified species and strengthened knowledge of the levels of COI variation both within and between species
Summary
DNA barcoding [1] of animals, the analysis of a standardized segment of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene, has rapidly become an important tool for the identification, delimitation, and discovery of species [1,2,3]. Its capacity to identify all life stages is important for aquatic ecology and biological monitoring (biomonitoring) of water quality because the aquatic larvae are usually the life stage studied [6]. This is the life stage that is the most poorly known taxonomically because most species concepts in aquatic insects are based on the morphology of adult males. In addition to allowing the identification of difficult specimens, barcoding provides a level of data standardization that has been previously lacking in environmental assessments [13], aiding broader comparisons of results gathered through monitoring programs. Barcoding reliably produces species-level (or even population-level) identifications that can improve the sensitivity of analyses, depending on the aims of the assessment program [14,15]
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