The Role of Transposable Elements in Speciation

Abstract

Understanding the phenotypic and molecular mechanisms that contribute to genetic diversity between and within species is fundamental in studying the evolution of species. In particular, identifying the interspecific differences that lead to the reduction or even cessation of gene flow between nascent species is one of the main goals of speciation genetic research. Transposable elements (TEs) are DNA sequences with the ability to move within genomes. TEs are ubiquitous throughout eukaryotic genomes and have been shown to alter regulatory networks, gene expression, and to rearrange genomes as a result of their transposition. However, no systematic effort has evaluated the role of TEs in speciation. We compiled the evidence for TEs as potential causes of reproductive isolation across a diversity of taxa. We find that TEs are often associated with hybrid defects that might preclude the fusion between species, but that the involvement of TEs in other barriers to gene flow different from postzygotic isolation is still relatively unknown. Finally, we list a series of guides and research avenues to disentangle the effects of TEs on the origin of new species.

Keywords: reproductive isolation; speciation; transposable elements.

Figure 1

A graphical classification of transposable elements (TEs). The left panel shows Class 1 retrotransposons, and the right panel shows Class 2 DNA transposons. The upper panels show three examples of the genetic structure of each of these two classes of elements. The lower panels show the mode of movement (transposition mechanism) of each class. LTR: Long Terminal Repeats; LINE: Long interspersed nuclear elements; SINE: Short interspersed elements.

Figure 2

Two possible scenarios that illustrate potential connections between TEs and the likelihood of introgression. Two species are illustrated (blue and red). Stripped bars show chromosomes that contain TEs, while solid bars are chromosomes with no TEs. The left panel (Scenario 1) shows a potential scenario in which TEs facilitate the transfer of a full chromosome. The right panel (Scenario 2) shows a potential scenario in which TEs cannot cross the species boundary and thus chromosomes that harbor them are less likely to be introgressed. For simplicity only one direction of introgression is shown.