A cytological study of two closely related blackfly species: Cnephia dacotensis and Cnephia ornithophilia (Diptera: Simuliidae)

Abstract

Cnephia dacotensis and C. ornithophilia are two closely related blackfly species. Their polytene chromosome complements differ in three interspecific inversions, in separate inversion polymorphisms, and the presence of specific sex chromosomes of C. dacotensis. These sex chromosomes comprise four structurally different X chromosomes and two structurally different Y chromosomes. A molecular model is proposed for their evolution. Light microscopy revealed that both species have male achiasmate meiosis. Male larvae of C. dacotensis lack synaptonemal complexes. Random association of inversions IIIS-1 and IIIL-1 and the presence of synaptonemal complexes indicate that crossing-over occurs in the female.