Common Bush-Tanager - Systematics and Taxonomy

Systematics and Taxonomy

Traditionally, the genus Chlorospingus was placed with the tanager family, Thraupidae. More recent research suggests that they are actually aberrant brush-finches in the Emberizidae and particularly close to Arremonops. Hence, as a common name "chlorospinguses" would arguably better than that the widely used "brush-tanagers", as the former is equally well suited to either placement.

The wide range and considerable morphological variation displayed by C. ophthalmicus has been a problem for ornithologists for many decades. Initially, many taxa presently united in this species were considered distinct, but they were eventually all lumped together. More recent results suggest that the "Common Bush-tanager" is actually a superspecies.

A preliminary study of allozyme data found pronounced divergences between the northern populations. mtDNA ATPase 8 sequence data found 5 major clades in the Mexican populations alone. These were subsequently confirmed by morphological comparisons. A formal splitting-up of this species into several seems to be the eventual outcome, pending data from the populations south of Mexico. In addition, it would be interesting to determine whether there are geographical variations in the song that would further strengthen the case for species status of the taxa. The morphological variation, though recognizable, is rather inconspicuous and probably more the consequence of genetic drift in freshly isolated subpopulations than a cause for their separation.