Setting a Standard for Species
NatureServe chief scientist Tom Brooks and Kris Helgen of the Smithsonian Institution’s National Museum of Natural History have published an review of Tobias et al., “Quantitative criteria for species delimitation” (Ibis 152: 724-746) that lauds a proposed framework for distinguishing between species and subspecies.
Delimitation of species is especially taxing when populations of similar organisms occupy non-overlapping geographical ranges, and in “A Standard for Species,” Brooks & Helgen describe how this new quantitative framework offers a consistent approach for tackling the problem. “Tobias et al. step beyond arguments over species concepts by standardizing criteria for distinguishing between subspecies and full species, especially to prevent trivial distinctions between populations from driving taxonomic inflation. Their proposal is to use the degree of differentiation between closely related bird species living in the same places without interbreeding (an accepted “gold standard” for recognition as separate species) as a yardstick to determine species status between those living apart.”