THE MARINER TRANSPOSABLE ELEMENT IN THE DROSOPHILIDAE FAMILY

The distribution of the mariner transposable element among Drosophilidae species was investigated using three different techniques, i.e. squash blots, Southern blots and PCR amplification, using two sets of primers (one corresponding to the Inverted Terminal Repeats and the other to two conserved regions of the putative transposase). Our results and those of others show that the distribution of mariner is not uniform and does not follow the phylogeny of the host species. An analysis of geographical distribution, based on endemic species, shows that mariner is mainly present in Asia and Africa. At least two hypotheses may be proposed to explain the specific and geographical distributions of this element. Firstly, they may be the results of several horizontal transmissions between Drosophila species and/or between Drosophila species and one or several donor species outside the Drosophilidae family. Secondly, these particular distributions may correspond to the evolution of the mariner element from an ancestral copy which was present in the ancestor of the Drosophilidae family.