Sir

Michael Patten, in his Correspondence stating that 'subspecies' and 'race' should not be used as synonyms (Nature 457, 147; 2009), claims that subspecies “remains a useful taxonomic division that enriches our understanding of evolution and biogeography”. But, as a classificatory unit, subspecies are not useful in comparative systematic and biogeographical studies because — unlike genera and families, for example — subspecies are groups of populations that are defined by hypothesized biological interactions or geographical distributions, rather than by homology (shared derived characteristics).

Patten says that his definition of subspecies is not arbitrary, “as there are clear ways of describing a subspecies objectively”. Yet there are no objective ways to describe species, let alone subspecies.

The species-concept debate is a result of many claiming to have found the 'objective' way to describe a species. So far, this has led to more than 25 species concepts. Patten's definition may therefore represent another addition to the already growing number of 'subspecies concepts'.