Courtship and mating time in Drosophila pseudoobscura

Abstract

Mating speed in Drosophila depends on courtship activity of males and receptivity of females with some variability from indeterminate causes. Copulation duration on the other hand is a constant and reliable portion of mating activity. In order to test the effects of certain genetic and environmental variables on mating activity in D. pseudoobscura, four strains (three Arrowhead and one Pikes Peak arrangement of the third chromosome) were studied: In the first tests F 1 and F 2 from strain crosses of AR AR were varied using heterogamic matings ( AR AR × AR PP ) in single pairs with AR PP serving as a ‘standard’. In the second set culture media and density of flies in the mating chamber were varied with homogamic combinations. Male activity in tune of courtship is strain-specific but not significantly affected either by age of parents within these experimental limits or by inbreeding one generation; the variance of this measure in the AR PP karyotype, which was uncontrolled for age of parents or density in culture, was much higher than for the AR AR karyotype which was controlled. The time to courtship is not completely determined by the male since AR AR males × AR PP females court faster than AR AR males to their own females. Female response is relatively unvarying in that all strains and generations of females tested were about equal in accepting males once courted (80 to 90 per cent). Consequently the percentage of total mating here depends on male propensity to courtship. Duration of copulation was the most uniform part of mating activity, quite strain-specific and male-determined as evidenced from reciprocal matings. There is no general relationship between courtship time and copulation time, there being no significant correlation between the two. Culture media during development and density of individuals in mating chambers (sexes equal in frequency) have no general effects though there are significant special interactions which are discussed in the light of need for flexibility under local conditions. Speed of mating then is not strictly controlled unconditionally by either sex although the duration of copulation is probably male-determined in this species. Control for the entire mating process is probably genetically conditioned and may be recognized by preponderantly greater emphasis on the courting and copulation tendencies of males vs. avoidance-acceptance responses of females.