Cytotype polymorphism of the P-M system in two wild populations of Drosophila melanogaster.

Abstract

In D. melanogaster the interactions of the P-M system generate germ-line aberrations (e.g., sterility, mutations) found in certain interstrain hybrids. Two wild populations, from France and Tunisia, were examined in order to determine the distribution of the chromosomal P factor and the extrachromosomal cytotypes. No P factors active for potential GD sterility were found in these populations. But search for the M cytotype, which causes susceptibility to the P factors, and for the P cytotype, which causes resistance to the P factors, showed that both populations are polymorphic for the cytotypes. Such a polymorphism seems to be stable in the wild, at least over a 2-yr period. Mutator activity (measured by generated mutations at the sn and ras loci) was present. Some possible interactions between cytotype polymorphism, mutator activity, and the structure of Drosophila populations are discussed.