THE SALIVARY GLAND CHROMOSOMES OF TWO SIBLING SPECIES OF BLACK FLIES INCLUDED IN EUSIMULIUM AUREUM FRIES

Abstract

Two closely related dichromosomic sibling species of Eusimulium "aureum" were segregated cytologically in populations sampled from the Toronto area. The known range of these two so far included southern Ontario and Quebec, and New York State. Both siblings have extremely similar salivary gland chromosomes but they differ by four homozygously rearranged regions, all in the first chromosome, and in the degree of chromosomal polymorphism. Although sympatric over a wide range, the two siblings do not interbreed as evidenced by the failure to find critical heterozygous loops for the interspecific inversions, and the absence of common intraspecific inversions. Therefore the siblings represent two biologically distinct species.