The evolutionary genetics of the hobo transposable element in the Drosophila melanogaster complex

Hobo elements are a family of transposable elements found in Drosophila melanogaster and its three sibling species: D. simulans, D. mauritiana and D. sechellia. Studies in D. melanogaster have shown that hobo may be mobilized, and that the genetic effects of such mobilizations included the general features of hybrid dysgenesis: mutations, chromosomal rearrangements and gonadal dysgenis in F1 individuals. At the evolutionary level some hobo-hybridizing sequences have also been found in the other members of the melanogaster subgroup and in many members of the related montium subgroup. Surveys of older collected strains of D. melanogaster suggest that complete hobo elements were absent prior to 50 years ago and that they have recently been introduced into this species by horizontal transfer. In this paper we review our findings and those of others, in order to precisely describe the geographical distribution and the evolutionary history of hobo in the D. melanogaster complex. Studies of the DNA sequences reveal a different level of divergence between the group D. melanogaster, D. simulans and D. mauritiana and the fourth species D. sechellia. The hypothesis of multiple transfers in the recent past into the D. melanogaster complex from a common outside source is discussed.