Selection against transposable elements inD. simulansandD. melanogaster

Abstract

SummaryThe insertion site numbers of the transposable elements (TEs) copia, mdgl, 412 and gypsy were determined in various natural populations ofDrosophila melanogasterandD. simulansby in situ hybridization. We showed that, while all elements except gypsy had many insertion sites scattered over the chromosomes inD. melanogaster, only the 412 element inD. simulanspresented a high number of insertions, and this number was lower than inD. melanogaster. This low 412 site number per genome inD. simulanswas associated with a lower proportion of insertions on the X chromosome in comparison withD. melanogaster, as determined in diploid genomes (0·090 forD. simulansagainst 0·137 forD. melanogaster) and in haploid genomes (0·102 against 0·146), each value being, moreover, lower than the value of 0·20 expected on the hypothesis of no selection against insertional mutations. These results suggest that selection is a major mechanism explaining 412 copy number regulation inDrosophila, and is stronger inD. simulansthan inD. melanogaster.