Approximate rates of accumulation for different genomic changes over evolutionary time. Details of the literature survey used to estimate these rates are provided in Additional file 2. The estimate of the avian microinversion rate reflects the results of this paper. Estimates of evolutionary rates for nucleotide substitutions and indels in birds appear lower than those for mammals, consistent with some previous publications , but it is important to note that substantial rate variation occurs within each group (e.g., [27, 60]). As described in the text, it may be better to interpret prior estimates of the mammalian microinversion rate as the rate at which relatively long microinversions accumulate.