Osamu Kitagawa

Chromosomal analysis and phylogenetic relationships in the Drosophila nasuta subgroup I. Phylogenetic relationships within the Drosophila sulfurigaster species complex

Phylogenetic relationships within the Drosophila sulfurigaster species-complex, which belongs to the D. nasuta subgroup, were investigated on the basis of chromosomal constitution and morphology. D. pulaua is thought to be the most ancestral species, from which D. s. sulfurigaster and D. s. bilimbata derived in one branch and D. s. albostrigata and D. s. neonasuta in another branch.

The failure to obtain sexual isolation by artificial selection

When strains of Drosophila melanogaster derived from Japanese and French natural populations were tested for mating preferences, one of three patterns was observed: panmictic, homogamic or selective mating. An attempt was made to select for increased sexual isolation between three pairs of the panmictic strains and four pairs demonstrating isolation or selection. None succeeded. However, an analysis of male and female selection points out no departure from panmixia in the panmictic strains and a selective mating tendency during the first 10 generations of selection in strains demonstrating isolation or selection. We hypothesize that the number of genes controlling sexual selection or isolation is small and that polymorphism for these genes varies from one strain to another.