Evolutionary patterns of the gypsy and bilbo retrotransposon families in the Drosophila species of the obscura group.

We analyse in this paper the evolutionary patterns of two types of Drosophila retrotransposons, gypsy (a virus-like element), and bilbo (a LINE-like element), in host species from the Drosophila and Scaptomyza genus. Phylogenetic analysis of the retrotransposon sequences amplified by PCR, revealed concordance with the phylogeny of the Drosophila host species from the obscura group, which is consistent with vertical transmission during differentiation of the species. However, in the species outside of the obscura group, horizontal transmission can be considered. The amplified sequences that presented intact open reading frames were used in an analysis of the evolutionary constraints on the amino acid sequences. The analysed sequences seem to be functional, and the selective constraints are evidenced, especially when sequences from distant species are compared. Comparison of the evolutionary rates of both retrotransposons in the same species, suggests that bilbo seems to evolve more rapidly than gypsy.