Your News Feature 'The species and the specious' (Nature 446, 250–253; 2007) provided an interesting assessment of recent research on genetics, species taxonomy and conservation.

Although mitochondrial DNA (mtDNA) and other molecular genetic data are informative, they must be viewed in the context of natural history and population biology. A strictly phylogenetic approach using genetic data may not consider the limitations of gene phylogenies or the relevance of organism-level data. The sciences of systematics, population genetics, phylogenetics and taxonomy require assessment of different types of data. As you note, boundaries between groups within species are not always clear, which has led to extensive assessment of the appropriate units for fish and wildlife management and conservation. I suggest that management should focus on a species' occurrence in geographical areas rather than seemingly endless debate over vague terms such as genetic discreteness or evolutionary legacy, and proliferation of new intraspecific terminology for what are essentially populations.

One example of this debate is provided in your News Feature, in which you note that there is similar mtDNA in polar bears and brown bears that brings their status as species into question. However, morphology, behaviour and habitats show these to be different species regardless of their mtDNA relationship; therefore management of polar bears and brown bears as separate species is appropriate.

The limitations of genetic data are apparent from the contrasting patterns of similar mtDNA in different species (polar bears and brown bears) and divergent mtDNA within populations of one species, black bears (M. A. Cronin et al. Can. J. Zool. 69, 2985–2992; 1991).