2.4.2. Tracking Biological Invasions

The field of conservation biology has also benefited from the accuracy of DNA barcoding methods to trace biological invasions. It has been estimated that the control of invasive species costs more than \$27 billion annually in the United States alone [170]. Fast detection can significantly reduce the cost of controlling biological invasions, and DNA barcodes and metabarcoding in particular have been demonstrated to provide the earliest invasive species detection methods available [171]. For example, one of the most widespread threats to marine ecosystems is the invasive zebra mussel, *Dreissena polymorpha*, and recent studies [172], using metabarcoding (or environmental DNA), have proven this method to be cost effective for early detection of this species in marine environments. Studies that quantify regional biodiversity using DNA barcodes have also proven effective for identifying biological invasions [173], where higher than expected phylogenetic diversity may result from the occurrence of non-native or invasive species.

In some groups of plants, invasive and weedy species are remarkably difficult to visually distinguish from non-invasive, endemic species, and several studies sugges<sup>t</sup> DNA barcoding will facilitate proper identification and managemen<sup>t</sup> by non-specialists. For example, current DNA barcodes in many plant taxa are unable to distinguish taxa at or below the genus-level, but new paradigms in barcode sequencing provide greater distinction of closely related species. Wang et al. [174] have advocated the use of super- or ultra-barcodes (e.g., whole chloroplast genomes) to monitor and detect flaxleaf fleabane, *Conyza bonariensis*, because, unlike traditional plant DNA barcodes, these super-barcodes are able to distinguish among closely related species in this diverse and difficult to identify genus.
