Taxonomic inflation: two additional causes

by Yehudah L. Werner

Department of Evolution, Systematics and Ecology, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel (e-mail:

The recent detailed and extensively documented review of taxonomic inflation, by Padial and De la Riva (2006) (doi:10.1080/1063515060081588), of necessity omitted two additional causes for the promotion of subspecies to species. Both causes are almost secret and of both I am only aware through personal involvement with taxonomy and, especially, taxonomists. For both it would be very difficult to collect quantitative data on the frequency of occurrence.

First, even if hard to believe, some new taxa are originally described as lowly subspecies, rather than species, merely out of â??modestyâ?. The taxonomist hesitates to claim the honor of having discovered a full species, or is loath, maybe unable, to invest the time and resources that would be required for convincingly erecting a species (e.g., with the biological species concept, show the extreme probability of reproductive isolation). With either motive, the taxonomist in effect â??economicallyâ? puts his name on the new taxon, leaving it to others to promote it to species level, when later this become indicated by the detailed circumstances.

A second hidden cause for promoting taxa from subspecies to species is conservation. I trust that only very few taxonomists would artificially, unjustifiably, erect species solely for the purpose of conservation. However, often it is legitimately debatable whether an established nominal subspecies deserves full species rank. Then the conscientious taxonomist, who always quests for the golden path between lumping and splitting, may (perhaps should) permit a known or expected conservation problem to guide him towards splitting, and promotes the subspecies to species.

On this occasion I should point out an error in Figure 1 of Padial and De la Riva (2006). Since the ordinate labeled â??Number of speciesâ? obviously refers to the cumulative number (not number of new species of that year), the abscissa, labeled â??Year of descriptionâ? should read â??Year of countâ? (or â??Yearâ?).

For further discussion of this topic, see Werner, Y. L. (2006), The case of impact factor versus taxonomy: a proposal, Journal of Natural History, doi:10.1080/00222930600903660.