Report of the Special-purpose Committee on DNA Sequences as Types, established at the XIX International Botanical Congress in Shenzhen, China

A Special-purpose Committee on DNA Sequences as Types was established at the XIX International Botanical Congress (IBC) in Shenzhen, China in 2017, with a mandate to report to the XX IBC with recommendations on a preferred course of action with respect to DNA sequences as potential types under the International Code of Nomenclature for algae, fungi, and plants. This report provides a synthesis of the deliberations from the Special-purpose Committee on this issue. We discuss two potential options for dealing with the problem that many species, especially of microfungi and microalgae, can be discovered and delimited using eDNA sequencing but cannot currently be formally named due to the requirement in the Code that either a specimen or illustration be nominated as holotype. One option is to expand the definition of "type" to include DNA sequences, while a second option would allow some taxa to be named without types, the application of their names instead being determined using a DNA sequence. This report should be read in concert with two formal proposals for potential amendments to effect these options, published in this issue of Taxon.