Rapid evolution of the Responder satellite in the melanogaster species subgroup. Amanda M. Larracuente, Daven C. Presgraves. Biology, University of Rochester, Rochester, NY.

   Responder (Rsp) is a satellite DNA repeat found in the pericentric heterochromatin of chromosome 2 in Drosophila melanogaster. Rsp is well-known for being the target of Segregation Distorter (SD)— a meiotic drive system found on chromosome 2 of D. melanogaster. We studied the evolution of this satellite in D. melanogaster and its close relatives. We find that Rsp is not a satellite cluster restricted to pericentric heterochromatin: Rsp repeats occur throughout the genome, including the euchromatin. Contrary to previous reports, we find the Responder satellite in D. simulans and D. sechellia. The repeats in these species are considerably diverged at the sequence level compared to D. melanogaster and have a strikingly different genomic distribution. Thus, Rsp has diverged in both sequence and genomic location on a short time scale of <240,000 years. We contrast the evolution of this satellite between one species where it is, and species where it presumably is not a target of segregation distortion.