R. Wang, J. Wakeley, and J. Hey. Genetics, 147 (3):
1091-1106(1997)In three species of Drosophila, looks at three different nuclear loci (two of which is on the X chromosome) and finds evidence of recent gene flow in one, but not in the other two. Cites mtDNA and allozyme studies as well, with differing conclusions..
M. Aguade, N. Miyashita, and C. Langley. Genetics, 122 (3):
607-615(July 1989)"In particular, the low genetic diversity seen in regions of low recombination in Drosophila and other organisms (Aguade et al. 1989; Aquadro et al. 1994) must be due to some kind of selection.".