Unique Incompatibility System in a Hybrid Species

Abstract

All males of the weevil Pissodes terminalis Hopp. are heterozygous for an autosomal fusion (cc --> C); all females are homozygous (CC). A mechanism is operative whereby union of like gametes gives rise to females and of unlike gametes gives rise to males, and union of half-alike gametes is totally excluded. The perpetuation of this sexual dimorphism of karyotypes following crossing implicates P. yosemite Hopk. in the hybrid origin of P. terminalis..