Critical Evaluation of DNA Hybridization Studies in Avian Systematics

It is frequently claimed that equal rates of DNA evolution are observed in birds, but specific tests necessary to demonstrate this are rarely performed. I demonstrated statistically significant differences in rates of DNA evolution for a few passerine birds that vitiate the role of DNA hybridization as the direct indicator of kinship. The differences in evolutionary rates observed may be substantial enough to introduce ambiguity into the clustering of taxa. Researchers frequently fail to perform the specific experiments needed to distinguish between real differences in relative rates of DNA evolution vs. differences that can be attributed to experimental error. They also fail to draw attention to and account for either erroneous or problematical data for some birds, or fail to perform the experiments necessary to determine the cause of unexpectedly problematical results. The DNA molecular clock is shown to be calibrated using speculative and questionable data. It involves diverse organisms that cannot be shown to evolve at the same rate, and that probably did not. Yet, DNA hybridization is a valuable tool that probably cannot lead one to make major systematic errors providing the data are not incorrect because of technical or computational errors and are taken from a sufficient diversity of relevant taxa.