Boosting Macroevolution: Genomic Changes Triggering Qualitative Expansions of Regulatory Potential

Abstract

Two main types of factors have been traditionally considered as potential driving forces underlying macroevolutionary patterns: environmental (“external”) cues and genetic and/or developmental (“internal”) factors. However, whereas the impact of non-gradual environmental changes has been extensively investigated, the contribution of internal causes, especially of genomic factors, has been approached in a less systematic manner, without clear definitions and classification schemes. Here, taking advantage of recent advances in comparative and functional genomics, we define three types of genomic changes that likely play important roles in macroevolutionary processes: (1) emergence of novel functional genomic properties, (2) large-scale genome reshaping and (3) qualitative single amplifications of regulatory potentials (which we term quasa-regs). Their unifying theme is their ability to qualitatively expand the genomic regulatory potential of the species. We review examples in which these types of changes have likely played important roles and discuss their potential macroevolutionary implications. We conclude that, although such changes may have a minor organismal impact at the time of emergence, they are likely to often have profound long-term effects by expanding regulatory abilities and opening new highways that boost the evolutionary process.