Distribution of transposable elements in Drosophila species

We present a global analysis of the distribution of 43 transposable element s (TEs) in 228 species of the Drosophila genus from our data and data from the literature. Data on chromosome localization come from in situ hybridiza tion and presence/absence of the elements from southern analyses. This anal ysis shows great differences between TE distributions, even among closely r elated species. Some TEs are distributed according to the phylogeny of thei r host specie; others do not entirely follow the phylogeny, suggesting hori zontal transfers. A higher number of insertion sites for most TEs in the ge nome of D. melanogaster is observed when compared with that in D. simulans. This suggests either intrinsic differences in genomic characteristics betw een the two species, or the influence of differing effective population siz es, although biases due to the use of TE probes coming mostly from D. melan ogaster and to the way TEs are initially detected in species cannot be rule d out. Data on TEs more specific to the species under consideration are nec essary for a better understanding of their distribution in organisms and po pulations.