Chromosomal Polymorphism in Drosophila Paramelanica Patterson

Abstract

carried out chiefly with Drosophila has revealed a wealth of chromosomal and genetic variability in natural populations, and in addition has begun to indicate some of the evolutionary relationships which exist between species, as well as the complex genetic systems which are responsible for the maintenance of the intraspecific chromosomal and genetic polymorphism.The Drosophila melanica species group appears to off er unusual opportunities for such studies. The members of the group are truly "wild", and unlike some domestic Drosophila species, are relatively little affected by man's activities. They occupy a broad geographical range, and the different species will in many instances cross to form fertile hybrids. Finally, at least some members of the group show a high degree of chromosomal polymorphism.For a number of years the author has been engaged in a long-term study of the interspecific chromosomal changes which have occurred in the evolution of this group, and as one of the necessary preliminary steps, a study of the intraspecific variation has been undertaken.Previously the only species in the group which had been thoroughly studied in regard to its chromosomal polymorphism was D. melanica melanica. In this species WARD (1952) studied salivary gland chromosomes derived from 65 laboratory strains, and found that the X chromosome showed four inversions differing from Standard, chromosome 4 showed two inversions and chromosome 2 showed 16. No inverted sequences were found in chromosomes 3 or 5. WARD also found that there were some differences in geographical distributions of the various gene sequences. It is the purpose of the present paper to report a series of cytological surveys carried out on Drosophila melanica paramelanica Patterson.PATTERSON (1943) split the species D. melanica Sturtevant into the two subspecies D. m. melanica and D. m. paramelanica on the basis of rather minor

CHROMOSOME INTERACTIONS IN DROSOPHILA ROBUSTA

“…Chromosome interactions affecting uiability: Intrachromosomal associations: Linkage disequilibria have been observed in many natural and laboratory populations of Drosophila species for marker genes and chromosome inversions (e.g., CANNON 1963;STALKER 1960STALKER ,1964LEVITAN 1958a).…”

A Model of Functional Epistasis and Linkage Disequilibrium in Populations With Overlapping Generations

“…There are numerous examples of nonrandom associations of inversions which occur in natural populations and are apparently due to epistatic fitness interaction (cf. LEVITAN, 1958;LEVITAN and SALZANO 1959;STALKER 1960). Such interactions have also been shown to act with respect to the other components of fitness-another requirement of the model.…”

EXPERIMENTAL DETERMINATION OF FITNESS INTERACTIONS IN DROSOPHILA MELANOGASTER BY THE METHOD OF MARGINAL POPULATIONS

“…Several observations support the relevance of this body of theory to natural and laboratory populations. Non-random associaticins of inversions in natural populations may be the result of fitness interaction between the inversions (LEVITAN, 1958;LEVITAN and SALZANO 1959;STALKER 1960; WHITE, LEWONTIN and ANDREW 1963). Viability interactions between inversions have been demonstrated experimentally ( SPASS-KY, DOBZHANSKY and ANDERSON 1965…”