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There is increasing evidence that mate recognition systems vary within species. We studied the courtship rituals of five Drosophila virilis strains to investigate this intraspecific variation. Males that actively and persistently courted the female without paying much attention to the female''s behaviour were the most successful at copulating. Intraspecific variation in mating rituals was high, but not as high as at the species level and it was not high enough to cause sexual isolation between the strains. The differences in courtship interactions of the strains reflected their geographical origin. Males from one of the strains did not produce audible song during their courtship, but still mated with some females of all strains. The courtships of the ‘mute’ males proceeded in the same way as those of the normal males, and the male''s wing vibration (even though silent and produced at a late stage) was still an important part of the courtship. [Copyright &y& Elsevier]

In the Drosophila virilis group the males of the virilis phylad species produce courtship song consisting of pulse trains with no pauses between successive sound pulses, whereas the males of the montana phylad species produce songs with clear pauses between the sound pulses. We obtained song data for F[sub 1] hybrids between D. virilis (representing the virilis phylad) or D. flavomontana (representing the montana phylad) females and the males of several species of the D. virilis group to study the interaction of X chromosomal and autosomal song genes affecting species differences in song. In crosses with D. virilis females, X chromosomal (or maternal) factors masked variation in pulse length despite variation in heterospecific autosomal song genes. To the contrary, in crosses with D. flavomontana females, X chromosomal genes largely determined the pause length and interacted with autosomal genes to determine the pulse length. In the montana phylad species, pulse length showed dominance toward shorter pulses and pause length toward longer pauses. The first-mentioned trait also indicated the epistatic effects of X chromosomal and autosomal components. [ABSTRACT FROM AUTHOR]

We studied genetic variation in fly mating signals and mate choice in crosses within and between inbred strains of Drosophila montana. Male songs and the cuticular hydrocarbons of both sexes as well as some of the flies’ behavioural traits differed significantly between strains. This did not, however, cause sexual isolation between strains. In fact, courtship was shorter if the female was courted by a male of a foreign strain than when courted by their own male. Heterosis was found for courtship duration and the carrier frequency of male song. Diallel analysis of male song revealed additive genetic variation in four out of the five traits studied. Two traits showed dominance variation and one of these, carrier frequency, expressed unidirectional dominance with alleles for higher carrier frequency being dominant. Direction of dominance in carrier frequency was the same as the direction of sexual selection exercised by D. montana females on this trait, which suggests that sexual selection could be a driving force in the evolution of song towards a higher carrier frequency. [ABSTRACT FROM AUTHOR]