Cytogenetics of the Holarctic black fly Simulium noelleri (Diptera: Simuliidae)

Abstract

The polytene chromosomes of Simulium noelleri from 16 sites in Armenia, Canada, England, Germany, Russia, and Sweden were analyzed. A standard map is proposed for the S. noelleri species-group that is 11 fixed inversions removed from the original standard map of the subgenus Simulium. Based on one shared subterminal inversion in the IIIL arm, the S. noelleri species-group is in a trichotomy with the S. bezzi and S. ornatum species-groups. Reproductive isolation of S. noelleri and S. decorum is demonstrated chromosomally at sites where both occur together. All analyzed populations of S. noelleri are considered conservatively to represent a single species, although at least three cytotypes are recognized, based primarily on different sex-chromosome systems. Cytotype A, representing the type species of S. noelleri, occurs in Germany, England, and western Russia. Cytotype B occupies Sweden and western Canada, emphasizing the intimate connection between the northern Nearctic and Palearctic simuliid faunas. Cytotype C is known only from Armenia.