THE SALIVARY GLAND CHROMOSOMES OF SEVEN FORMS OF BLACK FLIES INCLUDED IN EUSIMULIUM AUREUM FRIES

Abstract

Seven closely related cytological forms are known for the dichromosomic black fly E. "aureum". All these forms have extremely similar salivary gland chromosomes but they differ from each other by (1) the floating (intraspecific) rearrangements present, (2) the details of the sex-determining mechanisms, and (3) at least one homozygous (interspecific) inversion in the first chromosome. Six of these forms are accounted for as three sympatric sibling species pairs. Although certain allopatric forms may yet be identified as geographic variants of a polymorphic species, evidence is presented to show that all seven forms are biologically distinct species. Their phylogenetic interrelationships have been traced by means of the homozygous interspecific inversions.