The TEACL method of DNA-DNA hybridization: technical considerations.

This paper emanated from a conference concerning the value, accuracy, and technical considerations of DNA-DNA hybridization for evolutionary studies. Our laboratory has been performing the so-called TEACL (tetraethylammonium chloride) method, and we have amassed sufficient data to indicate that this method is very powerful if performed properly with correct analyses. Here we address five technical considerations: (1) We present empirical data that size correction for tracer length is legitimate and accurate. (2) We show that the error of delta Tm measurement does not significantly increase with increasing distance up to at least 10 degrees C. (3) The error distribution for delta Tm does not deviate from the expected normal distribution indicating parametric statistics are probably legitimate for analyses. (4) Using a known phylogeny we examined the resolving power of the technique by showing that at least five taxa can be correctly placed in phylogenies with a maximum delta Tm of 2.5 degrees C. (5) To date, all our data sets based on DNA-DNA hybridization are very robust with respect to analytical procedures in that every algorithm used on the data sets has yielded identical trees with nearly identical branch lengths. Nevertheless, we point out that theoretical analyses of distance data (as generated by DNA-DNA hybridization) are lacking, especially with regard to tests of the molecular clock hypothesis.