Microsatellites reveal male recombination and neo-sex chromosome formation in Scaptodrosophila hibisci (Drosophilidae)

In drosophilid flies, male recombination and neo-sex chromosome formation are rare. Following the genotyping of full-sib families with 20 microsatellite markers and subsequent cytological work, we found evidence of both male recombination and neo-sex chromosome formation in Scaptodrosophila hibisci. As far as we are aware, this is the first report of male recombination and neo-sex chromosome formation co-occurring in a drosophilid fly. Two autosomal loci, Sh29c and Sh90, showed aberrant segregation of male parental alleles. We describe how an autosomal fission followed by fusion of one of the autosomal fragments to the Y chromosome to create a Y₁Y₂X₁X₂/ X₁X₁X₂X₂ sex determination system provides the most parsimonious explanation of the patterns we observe. Male recombination was observed in three families, including autosomal linkage groups and the Y₁/X₂ linkage group. In addition to the X₁ linkage group, two autosomal linkage groups were identified.