¹Institut für Tierzucht und Genetik, Veterinärmedizinische Universität Wien, Josef Baumann Gasse 1, 1210 Wien, Austria

Correspondence: Christian Schlötterer, E-mail: christian.schloetterer@vu-wien.ac.at

Received 14 February 1999; Accepted 19 September 2000.

Abstract

The neo-sex chromosomes of Drosophila americana americana were formed by a centric fusion between the autosomal element B and the X chromosome. Previous work has shown that the neo-Y chromosome is not degenerated genetically and that there is no evidence for genetic differentiation between neo-X and neo-Y chromosomes at the sequence level. To further address the genetic differentiation between the neo-sex chromosomes, microsatellites mapping to the neo-sex chromosome of D. a. americana were isolated. Microsatellite analysis indicated a highly significant differentiation between D. a. americana and D. a. texana as well as between the neo-X and neo-Y chromosomes in D. a. americana. Nevertheless, levels of variability were similar among the neo-sex chromosomes, indicating a very recent origin.