Tirant stealthily invaded naturalDrosophila melanogasterpopulations during the last century

Abstract

AbstractIt was long thought that solely three different transposable elements - the I-element, the P-element and hobo - invaded naturalD. melanogasterpopulations within the last century. By sequencing the ‘living fossils’ ofDrosophilaresearch, i.e.D. melanogasterstrains sampled from natural populations at different time points, we show that a fourth TE, Tirant, invadedD. melanogasterpopulations during the past century. Tirant likely spread inD. melanogasterpopulations around 1938, followed by the I-element, hobo, and, lastly, the P-element. In addition to the recent insertions of the canonical Tirant,D. melanogasterstrains harbour degraded Tirant sequences in the heterochromatin which are likely due to an ancient invasion, possibly predating the split ofD. melanogasterandD. simulans. In contrast to the I-element, P-element and hobo, we did not find that Tirant induces any hybrid dysgenesis symptoms. This absence of apparent phenotypic effects may explain the late discovery of the Tirant invasion. Recent Tirant insertions were found in all investigated natural populations. Populations from Tasmania carry distinct Tirant sequences, likely due to a founder effect. By investigating the TE composition of natural populations and strains sampled at different time points, insertion site polymorphisms, piRNAs and phenotypic effects, we provide a comprehensive study of a natural TE invasion.