DNA barcoding and taxonomy: dark taxa and dark texts

Both classical taxonomy and DNA barcoding are engaged in the task of digitising the living world. Much of the taxonomic literature remains undigitised. The rise of open access publishing this century, and the freeing of older literature from the shackles of copyright has greatly increased the online availability of taxonomic descriptions, but much of the literature of the mid- to late twentieth century remains offline ("dark texts"). DNA barcoding is generating a wealth of computable data that in many ways is much easier to work with than classical taxonomic descriptions, but many of the sequences are not identified to species level. These "dark taxa" hamper the classical method of integrating biodiversity data using shared taxonomic names. Voucher specimens are a potential common currency of both the taxonomic literature and sequence databases, and could be used to help link names, literature, and sequences. An obstacle to this approach is the lack of stable, resolvable specimen identifiers. The paper concludes with an appeal for a global "digital dashboard" to assess the extent to which biodiversity data is available online.