Symmetrical and asymmetrical sexual isolation among laboratory strains of Drosophila ananassae

Male-choice experiments using five isofemale lines of Drosophila ananassae originating from different localities were performed to study sexual isolation within the species. In most of the crosses homogamic matings outnumber heterogamic ones, and deviation from randomness is statistically significant in 11 of 20 crosses. This provides evidence for positive assortative mating within D. ananassae. Isolation indices range from −0.057 to 0.555. Eleven positive isolation indices are significantly greater than zero. Both types of sexual isolation, symmetrical and asymmetrical, have been observed among different strains. Thus the present results clearly indicate that the laboratory strains of D. ananassae have developed behavioural reproductive isolation as a result of genetic divergence.Key words: Drosophila, assortive mating, sexual selection, behaviour.

Assortive Mating in Later Life: Some Initial Considerations

BASED on initial concerns expressed in this article over lack of information on assortive mating in later life, a theoretical model of structural and attitudinal variables is developed for utilization in the comparative study of endogamy and homogamy. Exploratory data are presented to compare mating parameters between the young and the old and between older men and older women. From this effort, it is concluded that information about young adults' courtship contexts and mate selection cannot necessarily be generalized to courtship and marriage in later life and that additional, more refined, investigation into the latter area would be fruitful conceptually and pragmatically.