What can biological barcoding do for marine biology?

The idea of using nucleotide sequences as barcodes for species identification has stirred up debates in the community of taxonomists and systematists. We argue that barcodes are potentially extremely useful tools for taxonomy for several reasons. Barcodes may, for example, help to identify cryptic and polymorphic species and give means to associate life history stages of unknown identity. Barcode systems would thus be particularly helpful in cases when morphology is ambiguous or uninformative and would provide tools for higher taxonomic resolution of disparate life forms. Comparative analysis of short DNA sequences may also represent heuristic access cards to a deeper understanding of evolutionary relationships between organisms. However, barcodes are the "essence'' of species identities no more than taxonomic holotypes are "the species''. It makes no sense to think that morphology and other biological information about organisms can be made obsolete by barcode systems. The biological significance of matching or diverging nucleotide sequences will still have to be the subject of taxonomic decisions that must be open for scrutiny. It is imperative, therefore, that barcodes are associated with specimen vouchers.