Variation of priming sites vertebrates. Variation in priming sites of 16S rRNA (a, F-primer; b, R-primer) and COI (c, Bird-F1, LCO1490; d, HCO2198; e, Bird-R1, Bird-R2) fragments studied herein. Values are nucleotide variability as calculated using the DNAsp program. Grey bars show the values for nine amphibians, black bars the values for a set of 59 other vertebrates (see Materials and Methods, and Figs. 3-4).