Transposable elements: all mobile, all different, some stress responsive, some adaptive?

Transposable elements (TEs) were first identified through the polymorphisms they induced in plants and animals. Genomic studies have later revealed that TEs were highly abundant in eukaryotic genomes. Recently, more precise single individual genomic analyses have unravelled the huge diversity of TE insertions in many plant and animal species. In most cases the stress conditions behind this diversity are not known and neither is the adaptive capacity of these natural TE-induced variants. Here, we review some of the most recent examples of TE-related impacts on gene expression at the locus or the genome level and discuss the rich diversity of the TE repertoire and its potential role in adaptive evolution.