Abstract
DNA barcoding has become a promising means for identifying organisms of all life stages. Currently, phenetic approaches and tree-building methods have been used to define species boundaries and discover ‘cryptic species’. However, a universal threshold of genetic distance values to distinguish taxonomic groups cannot be determined. As an alternative, DNA barcoding approaches can be ‘character based’, whereby species are identified through the presence or absence of discrete nucleotide substitutions (character states) within a DNA sequence. We demonstrate the potential of character-based DNA barcodes by analysing 833 odonate specimens from 103 localities belonging to 64 species. A total of 54 species and 22 genera could be discriminated reliably through unique combinations of character states within only one mitochondrial gene region (NADH dehydrogenase 1). Character-based DNA barcodes were further successfully established at a population level discriminating seven population-specific entities out of a total of 19 populations belonging to three species. Thus, for the first time, DNA barcodes have been found to identify entities below the species level that may constitute separate conservation units or even species units. Our findings suggest that character-based DNA barcoding can be a rapid and reliable means for (i) the assignment of unknown specimens to a taxonomic group, (ii) the exploration of diagnosability of conservation units, and (iii) complementing taxonomic identification systems.
Highlights
To reliably identify and monitor biodiversity in the field and pinpoint more efficiently small but important areas of conservation is still a major challenge
Establishing DNA barcodes to identify previously defined groups of organisms at any taxonomic level is a powerful application of modern technology to biodiversity study
We achieved the first step for character-based DNA barcoding by highlighting the principal potential and effectiveness for identifying diagnostic DNA barcodes at different taxonomic levels
Summary
To reliably identify and monitor biodiversity in the field and pinpoint more efficiently small but important areas of conservation is still a major challenge. 3. RESULTS (a) Character-based DNA barcodes for odonate species Table 1 shows the character states at 23 nucleotide positions of the ND1 gene region for 14 species of the family Coenagrionidae. (c) Character-based DNA barcodes identifies entities at the population level ND1 sequences of members of 14 species of the family Coenagrionidae were selected from our original dataset, including 13 species of the genus Pseudagrion and one species of the genus Teinobasis. For extracting character-based DNA barcodes for single populations, the relevant nodes within the species cluster in the NJ tree (figure 1) were selected by means of the CAOS-group file and pure CAs for the groups descending from these nodes were extracted from the ‘diagView_attributes’ file. For the third Kenyan population from the Aberdare Mt. and the Tanzanian population from Kilimanjaro, the high number of 15 pure CAs was detected
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