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Studies of the variance and covariance between female mating preferences and sexually selected male traits in natural populations are rare. In D. montana, male courtship song is an important target of sexual selection. We analysed the variance in components of song and preferences among F1 families from a natural population. All song traits varied substantially, with among-family variance components ranging from 30 to 65%. The greatest variation was in carrier frequency, which is the most important predictor of mating success. This is compatible with the trait capturing mutational and other components of genetic variance in condition because of condition-dependent expression. There was also variation for some components of preference variation, with significant variation among sisters within families, and among families. Females varied in overall responsiveness, but not in the slope of the linear female preference function for male song carrier frequency. Such variation might be expected to generate assortative mating, with more choosy females mating with higher quality males, but there was no covariance across families between female responsiveness and male carrier frequency. Substantial variation in the level of responsiveness might allow low-quality males to achieve some mating success and counteract the build-up of a strong genetic covariance between preferences and traits.

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.

The courtship song of Drosophila is thought to be involved in sexual selection and species recognition. Because of the mating system of flies, however, directly demonstrating that song influences female preference is difficult. The majority of previous studies have used an experimental design that potentially confounds male and female reactions to song. In D. montana, correlational evidence has suggested that males that produce short sound pulses consisting of a high number of sound cycles (i.e. a high carrier frequency) have a higher mating success than other males. In this study, we played synthetic song that varied in pulse length and carrier frequency to individual females in the laboratory, both alone and in the presence of mute males. We scored female preference via an acceptance posture, 'wing spreading', which the females of this species usually display prior to mounting by a male. Females responded to synthetic song in the absence of males. The presence of mute males significantly increased their overall responsiveness, but the relative effectiveness of the songs did not change, eliminating male reaction to song as a possible confounding factor in the results. The interaction between pulse length and carrier frequency determined the discrimination between song types, with females responding most readily to song consisting of short pulses with a high carrier frequency. Thus, direct examination of female preferences supports the previous studies of male mating success, and confirms female song preference as a likely determinant of male mating success. Copyright 1998 The Association for the Study of Animal Behaviour

Drosophila planitibia , D. heteroneura and D. silvestris are the three most recently evolved species of the Hawaiian picture-winged D. planitibia subgroup. Drosophila planitibia from Maui is the presumed ancestor of the other two species, which occur partly sympatrically on the island of Hawaii. Drosophila silvestris is split into two morphologically different populations. The behaviour of the flies of these species/populations in successful and unsuccessful courtships was investigated. The most crucial differences between species were found in female responses (standing and walking) to male circling and in male responses to female standing and walking. Differences between D. silvestris strains were small compared with species differences. There were major differences between successful and unsuccessful matings in the response patterns most characteristic of different species.

The courtship sequences of wild-caughtDrosophila silvestrismales paired with virgin females (the daughters of wild-caught females) were studied in the laboratory to examine behavioural characters affecting male mating success. Successful males courted the female persistently (without breaks) and spent more time in the head-under-wings position and in wing vibration than unsuccessful males. The relative durations of head-under-wings and wing vibration appeared to be consistent within males. Females were active and vigorous participants in courtship, contrary to the stereotype of femaleDrosophilabeing passive observers of male displays. The females could interrupt the courtship by flying away from the courting male, but they often returned to the male waving their wings. Receptive females waved their wings, and spent more time standing and less time preening than unreceptive females. After slashing at the male (or as a reaction to male circling) they stood still more often than unreceptive females. It appears that although receptive females do not have a particular signal that invariably indicates receptivity, they encourage male courtship throughout the sequence, by being active early, and standing still later. These results will serve as a baseline for comparisons with other species, and to stimulate experiments to examine female mating preferences.

Abstract. The Drosophila planitibia subgroup belongs to the endemic Hawaiian picture-winged Drosophila species group. The males of this subgroup may produce sounds by fanning or vibrating their wings or by bobbing the abdomen. These wing songs fall into three categories: pulse song, phrase song and sound bursts. Among the most primitive species only D. obscuripes males produce sounds: a low-frequency phrase song. In one intermediate species D. neoperkinsi , the males produce all three songs, while in the other species the males use different combinations of the songs: only the phrase song, the pulse song plus the phrase song or the pulse song plus the sound burst. The males of the advanced species produce only sound bursts. The fact that the males of different lineages use similar kinds of songs in their courtship suggests that all three songs have evolved before the evolution of the intermediate and advanced species. During the speciation processes some of the wing songs have been omitted from the courtship rituals of the evolving species, while the remaining songs have become less variable and more species-specific.

In Drosophila montana (a species of the D. virilis group) the sounds produced by the courting male are a prerequisite for copulation. The mating behaviour of four experimental groups was recorded. Two groups consisted of single pairs of normal flies with successful and unsuccessful courtship, respectively. The third group consisted of single pairs of normal males and deaf females and the fourth group of single pairs of mute males and normal females. In successful courtships (i.e. those ending in copulation) touching and licking by the male led to female standing. Female standing led to male wing vibrating, male wing vibrating to female wing lifting, and female wing lifting to copulation. In unsuccessful courtships, the males did not vibrate their wings in response to female standing. In the groups lacking male auditory signals (deaf females or mute males) the females hummed their wings in response to male licking and wing vibrating. Although the males responded to wing humming by more licking and by producing more sounds, the courtships did not proceed to copulation. It is concluded that the willingness of the female to mate with a conspecific male depends on the detection of sound at the appropriate time in the courtship sequence as a response to female behaviour.

To study the variation and consistency of song preferences in Drosophila virilis females, we played them species-specific song and songs with modified sound pulses and/or interpulse intervals on 3 consecutive days. Species-specific song was played again on the fourth day. All playbacks were done without the presence of males. About 62% of the females indicated their readiness to mate by spreading their wings in at least one of the trials. The proportion of the females responding to species-specific song was about twice that of the females responding to modified songs. The majority of females responded to only one song type, which suggests that the females varied in their preferences and that their preference windows were rather narrow. The females were consistent in their responsiveness to species-specific song played on 2 days. If the female responded to normal song during the first trial, the probability of her responding to the same song during the second trial increased by about 32%. The number of songs required by the females before responding in the two subsequent trials was also correlated within the females (repeatability 0.328). Repeatability of female preferences for male sexual traits is expected both in the viability and Fisherian models of sexual selection. Copyright 1999 The Association for the Study of Animal Behaviour.

The courtship behaviour of four sympatric species of the Drosophila virilis group was studied in the wild, with most observations made at baits of fermenting malt. The males courted the females of both their own and alien species, but only intraspecific courtships occasionally led to a copulation. Nearly all of the interspecific courtships broke off when the female began to vibrate her wings or flew away shortly after the male had begun to make courtship sounds.

In this study, it is shown that the males of several picture-winged Drosophila subgroup species produced high-frequency clicking sounds when courting females. At the beginning of the courtship, the males may semaphore or vibrate their wings with a large amplitude, producing no audible sounds. After these ‘preliminary’ wing vibrations the males set their wings backwards in a normal resting position and vibrate them with a small amplitude, producing loud clicking sounds (up to 15000 cps), which differ from all Drosophila sounds described so far in both their spectral and their temporal structure. When producing these sounds the males always touch the abdomen of the female with their front legs, which might help the females receive the sounds as vibrational signals.