Sequences homologous to the P mobile element of Drosophila melanogaster are widely distributed in the subgenus Sophophora

Abstract

The biological properties of the P element of Drosophila melanogaster differ from those of other mobile elements in this genus in that its mobility is associated with dysgenic traits that might be expected to limit its distribution or spread¹. The P element is widely distributed among natural populations of D. melanogaster, but is absent from strains that have been maintained in the laboratory for more than thirty years². This observation prompted speculation that the P element has recently invaded and spread horizontally through D. melanogaster^3,4, a hypothesis supported by the observation that P elements are absent from the D. melanogaster sibling species⁵. However, sequences homologous to P elements have been found recently in Drosophila paulistorum, a quite distant relative⁶. This finding undermines any simple hypothesis about the origin of P elements, and demands a thorough analysis of the distribution and conservation of the P element within the subgenus Sophophora. We show here that the P element is present in every species group in the subgenus Sophophora, but that its distribution within species groups can be discontinuous. The P homologues from different species are not identical; furthermore, their genomic localization differs from that found in D. melanogaster.