Pleistocene speciation and the mitochondrial DNA clock
- B. J
- Science (Technical
Recently, Heindl & Schuchmann (1998) published a detailed speciation scenario for Metallura hummingbirds. They suggested a scenario where the three main lineages of Metallura, and the sister genus Chalcostigma, all dispersed out of an area of origin in the Andes of Bolivia or south eastern Peru, with successive pulses of dispersal northwards and intermittent isolation of populations during the last twoglacial periods. A fairly detailed sequence of events is suggested. The results and interpretations of a molecular phylogenetic study of the same group (Garcfa-Moreno et al. in press) are mentioned in a final paragraph ('Alternative model and time scale'). This study also suggests a southern origin of the group, but provides evidence of strong population subdivision, especially of taxa inhabiting treeline habitats (the M. aeneocauda species group, including the aberrant M. phoebe) since well before the onset of major glacial cycles 800,000 years ago. We would like to comment on some of the discrepancies between these two analyses of the same taxonomic group. 1) Heindl & Schuchmann contend the usefulness of the mtDNA data as a molecular clock.