Transposable elements activity reveals punctuated patterns of speciation in Mammals

Abstract

Transposable elements (TEs) play an essential role in shaping eukaryotic genomes and generating variability. Our \"Cold Genome\" hypothesis postulates that speciation and TEs activity are strongly related in mammals. In order to test this hypothesis, we created two new parameters: the Density of Insertion (DI) and the Relative Rate of Speciation (RRS). The DI is the ratio between the number of TE insertions in a genome and its size, whereas the RRS is a conditional parameter designed to identify potential speciation bursts. Thus, by analyzing TEs insertions in mammals, we defined the genomes as \"hot\" (low DI) and \"cold\" (high DI). Then, comparing TEs activity among 16 intra-order pairs of mammalian species, 4 superorders of Eutheria and 29 taxonomical families of the whole Mammalia class, we showed that taxa with positive RRS correlate with \"hot\" genomes, whereas taxa with negative RRS correlate with \"cold\" genomes. In addition, our study supports the \"Punctuated Equilibria\" theory in mammals for both adaptive radiation and stasis.