DNA Barcoding the Canadian Arctic Flora: Core Plastid Barcodes (<i>rbcL</i> + <i>matK</i>) for 490 Vascular Plant Species

<div><p>Accurate identification of Arctic plant species is critical for understanding potential climate-induced changes in their diversity and distributions. To facilitate rapid identification we generated DNA barcodes for the core plastid barcode loci (<i>rbcL</i> and <i>matK</i>) for 490 vascular plant species, representing nearly half of the Canadian Arctic flora and 93% of the flora of the Canadian Arctic Archipelago. Sequence recovery was higher for <i>rbcL</i> than <i>matK</i> (93% and 81%), and <i>rbcL</i> was easier to recover than <i>matK</i> from herbarium specimens (92% and 77%). Distance-based and sequence-similarity analyses of combined <i>rbcL</i> + <i>matK</i> data discriminate 97% of genera, 56% of species, and 7% of infraspecific taxa. There is a significant negative correlation between the number of species sampled per genus and the percent species resolution per genus. We characterize barcode variation in detail in the ten largest genera sampled (<i>Carex</i>, <i>Draba</i>, <i>Festuca</i>, <i>Pedicularis</i>, <i>Poa</i>, <i>Potentilla</i>, <i>Puccinellia</i>, <i>Ranunculus, Salix</i>, and <i>Saxifraga</i>) in the context of their phylogenetic relationships and taxonomy. Discrimination with the core barcode loci in these genera ranges from 0% in <i>Salix</i> to 85% in <i>Carex</i>. Haplotype variation in multiple genera does not correspond to species boundaries, including <i>Taraxacum</i>, in which the distribution of plastid haplotypes among Arctic species is consistent with plastid variation documented in non-Arctic species. Introgression of <i>Poa glauca</i> plastid DNA into multiple individuals of <i>P. hartzii</i> is problematic for identification of these species with DNA barcodes. Of three supplementary barcode loci (<i>psbA–trnH</i>, <i>psbK–psbI</i>, <i>atpF–atpH</i>) collected for a subset of <i>Poa</i> and <i>Puccinellia</i> species, only <i>atpF–atpH</i> improved discrimination in <i>Puccinellia</i>, compared with <i>rbcL</i> and <i>matK</i>. Variation in <i>matK</i> in <i>Vaccinium uliginosum</i> and <i>rbcL</i> in <i>Saxifraga oppositifolia</i> corresponds to variation in other loci used to characterize the phylogeographic histories of these Arctic-alpine species.</p>