GC₃ heterogeneity and body temperature in vertebrates

A recent paper by Belle et al. (J. Mol. Evol. 55 (2002) 356) reported an analysis of mean GC₃ (the GC level of third codon positions) and standard deviations of GC₃ of vertebrate genomes as related to body temperature, and concluded that "the thermal stability hypothesis does not appear to explain the general patterns of composition", apparently contradicting a previous working hypothesis from our laboratory. We have analyzed the data of Belle et al. and find that their data not only do not contradict the thermal stability hypothesis, but if anything support it.