Abstract
AbstractA DNA barcode consists of a standardized short sequence of DNA (400-800bp) used to identify the taxonomic species a small organic fragment belongs to. Even though it has been easy to discriminate animal species by using the mitochondrial gene cox1, this is still difficult for plants seeing that the mitochondrial genome is not variable enough on the species level. During the Second International Barcode of Life Conference in Tapei (September 2007), different plastid regions were proposed as potential plant DNA barcodes, such as atpF-atpH and psbK-psbI, but no consensus on which region to use was reached during the meeting. The largest plant DNA barcoding study to date proposed matK as the best candidate and suggested that in combination with trnH-psbA a slight increase in performance could be achieved. However, no study has tested the suitability of the newly proposed psbK-psbI and atpF-atpH for plant barcoding purposes. Four potential DNA barcodes, matK, trnH-psbA, atpF-atpH, and psbK-psbI, were amplified and sequenced for a selective sampling including mainly trees and shrubs of the flora of the Kruger National Park Africa (South Africa). The performance of each region and also each possible combination of these were tested by applying a battery of metrics and statistical tests. Our results confirm that the second half (5’ end) of matK is the best candidate in a single locus barcoding approach reaching 87.5% of species correctly identified. Combining matK with trnH-psbA and psbK-psbI increased only slightly the performance in discriminating species. The results from this study show that the use of a ‘three-region barcode’ does not significantly outperform matK in a single-locus barcoding approach. We therefore argue against the ‘multiple barcode approach’ proposed by the plant working group, and instead propose to keep barcoding plants in line with the approach taken for animals, i.e. using one barcode: cox1 for animals and matK for plants.
Highlights
DNA barcoding is a new technique that uses short, standardized DNA sequences (400-800 bp) of an organism to determine its identity
Because this sequence has to be variable enough to identify individual species, but not too variable within the same species so that a clear threshold can be defined between intra- and inter-specific diversities, it is very challenging to apply this technique to all species on the planet
A DNA barcode has been identified for animals, i.e. the mitochondrial gene cox1, which shows strong abilities in identifying cryptic species, accelerating biodiversity inventories and helping to identify species from degraded material
Summary
DNA barcoding is a new technique that uses short, standardized DNA sequences (400-800 bp) of an organism to determine its identity. At the Second International Barcode of Life Conference in Tapei (September 2007), at least five different plant DNA barcodes were proposed , but no consensus reached. Among those, both atpF-atpH and psbK-psbI suggested by Kim et al have not yet been tested. The genes atpF and atpH encode ATP synthase subunits CFO I and CFO III, respectively Both genes psbK and psbI encode two low molecular mass polypeptides, K and I, respectively, of the photo-system II. These two new loci are conservative from algae to land plants and even in parasitic plants. On a selected sampling from the 2,700 taxa surveyed in the area, we applied several metrics following Lahaye et al to evaluate the efficiency of combining matK either to trnH-psbA and/or atpF-atpH and/or psbK-psbI for DNA barcoding purposes
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