Crossing over between linked inversions in Drosophila ananassae

In Drosophila ananassae two linked inversions located in the opposite limbs of the third chromosome are of common occurrence in natural populations as well as in laboratory stocks. By utilising different stocks homozygous for the standard or inverted gene sequences in the second and third chromosomes, the rate of crossing over between linked inversions when heterozygous was studied under different karyotypic backgrounds in both sexes by means of the salivary gland smear technique. In spite of the long chromosome distance between them, the crossover rate is very low and it varies in different strains. Furthermore, there is a considerable increase of recombination between heterozygous inversions due to inversion heterozygosity in 2L, indicating interchromosomal effect. These findings provide evidence that recombination between linked inversions in D. ananassae is influenced by background karyotype and background genotype.