Experimental evidence for pseudo-arrhenotoky in Hypothenemus hampei (Coleoptera: Scolytidae)

Species breeding under local mate competition conditions have sex ratios biased towards females, a trait that is often associated with male haploidy (arrhenotoky). We used insecticide resistance as a genetic marker in Hypothenemus hampei, a local mate competing scolytid beetle that is cytologically diplo-diploid, for investigating the inheritance of nuclear genes. We confirmed that males express the resistance phenotype that they inherit from their mother, whatever their father. The segregation of resistance phenotypes in F-2 females significantly departed from the Mendelian model, and were in accordance with the arrhenotokous model, indicating that the parental genes were eliminated between F-1 and F-2. This finding (pseudo-arrhenotoky) constitutes a step towards an understanding of the mechanism by which diplo-diploidy evolves to arrhenotoky in local mate competing insects.