Polytene chromosomes of three species of blackflies in the Simulium pictipes group (Diptera: Simuliidae)

Abstract

BEDO, D. G. 1975. Polytene chromosomes of three species of blackflies in the Simuliumpictipes group (Diptera: Simuliidae). Can. J. Zool. 53: 1147-1 164. The salivary gland chromosomes of members of the Simulium pictipes group were examined by conventional staining and quinacrine fluorescence staining methods which proved to be a useful tool to show otherwise hidden details, especially in expanded centromere regions. Three cytologically definable species were found, one of which must represent a previously unrecognized species. Simulium longistylatum Shewell was the only species among the three siblings identified with certainty. The remaining pair were designated as S. pictipes A and S. pictipes B. In all three siblings the haploid chromosome number was three. Specific differences include a simple and a complex inversion, a shift of basal bands between the short arms of the second and third chromosome, details of the sex chromosomes, and the amount of DNA in certain individual bands and expanded centromere regions. Y chromosome markers are located in a different element of the complement in each of the three species, a unique situation within closely related blackfly sibling species. These findings are discussed in connection with the evolution of sex chromosomes and sibling species. A cytophylogeny is presented.BEDO, D. G. 1975. Polytene chromosomes of three species of blackflies in the Simulium pictipes group (Diptera: Sirnuliidae). Can. J. Zool. 53: 1 147-1 164. On a examine les chromosomes des glandes salivaires chez des individus du groupe Simulium pictipes par des mtthodes classiques de coloration et des methodes de coloration fluorescente a la quinacrine; ces methodes mettent en evidence certains details ordinairement invisibles, particulierement dans les rkgions renflees du centromere. On reconnait cytologiquement trois especes dont I'une est tres certainement une esptce inconnue jusqu'ici. Des trois especes jumelles, Simulium longistylatum est la seule a pouvoir btre identifiee avec certitude. On dCsigne les deux autres especes par les termes S . pictipes A et S . pictipes B. Chez les trois especes, le nombre chromosomique haploide est de trois. Parmi les differences spkcifiques, on compte une inversion simple et une inversion complexe, un transfert des stries basales entre les portions courtes du second et du troisieme chromosomes; il y a egalement de ltgtres differences entre les chromosomes sexuels et enfin certaines stries individuelles de mbme que les renflements du centromere contiennent des quantites differentes d'ADN. On a decouvert aussi un caractere differentiel unique entre des especes tres parentes de mouches noires jumelles: les marqueurs du chromosome Y sont situks dans un Clement different du complement chez chacune des trois espkces. La discussion porte sur I'Cvolution des chromosomes sexuels et des especes jumelles.

C-banding and chromosome evolution in some related species of Australian chironominae

“…australis the X chromosome was cytologically marked by C-bands which were not present in the Y. Such sex-linked heterochromatic bands or blocks are not uncommon in lower DiPtera and may mark the female sex chromosome (Newton et al, 1974, Bedo, 1975b, Procunier, 1975, Amabis, 1977 as in the present case, or may be found on the male sex chromosome (Rempel et al, 1962, Rosin & Fischer, 1972, Newton et al, 1974, Newman, 1977. In Chironomidae, sex-linked inversion sequences appear to be more common than heterochromatic blocks (e.g.…”

Chromosomal relationships of Simulium suzukii, an Old World member of the Simulium tuberosum species group (Diptera: Simuliidae)

“…A significant di#erence in the genotypic frequencies of one of the three autosomal inversions evaluated might reflect a tendency for females to return to the natal streams to oviposit. Stream-specific cytogenetic profiles of some species, for example, have suggested a greater tendency for ovipositing females to move along streams rather than between them (Bedo, 1975).…”

Cytogenetics of New Zealand blackflies of the genus Austrosimulium (Diptera: Simuliidae) II. Heterozygote deficiency and non-random association of inversion heterozygotes

“…Cryptic species based on the presence of these three criteria have been recorded by Dunbar (1958Dunbar ( , 1959Dunbar ( , 1966Dunbar ( , 1967, Ottonen and Nambiar (1969), Bedo (1975Bedo ( , 1977, Rothfels et al (1978), and Procunier (1982b). In the Simulium tuberosurn complex (Landau, 1962;Mason, 1982) the suggestion of cryptic species is based on differential sex chromosomes and differences in inversion polymorphisms only.…”