Morphological comparison among Drosophila lini and its two new sibling species (Diptera: Drosophilidae)

Morphological differences are investigated using several culture strains of three sibling species collected from Taiwan and Guangdong in China and Pyinoolwin and Yangon in Myanmar. Careful examination of male terminalia reveals distinguishable differences in the paramere and the aedeagal basal process among the three species. In addition, a number of quantitative characters are compared. Kruskal-Wallis tests with Bonferroni correction, which are carried out separately for each sex, detect significant differences in 15 characters, of which two are male-specific, among the three species. Canonical discriminant analysis using these characters reveals that the three species can be distinguished from each other with high confidence for both sexes. The results clearly show the presence of three good species, Drosophila (Sophophora) lini Bock & Wheeler, 1972 and its two new siblings. The new species are described as Drosophila (Sophophora) ohnishii sp. nov. from Pyinoolwin and Drosophila (Sophophora) ogumai sp. nov. from Yangon. The morphological differentiation among the three sibling species does not coincide with the degree of reproductive isolation (based on a previous study). The premating isolation pattern suggests two possibilities that premating isolation has been evolved or reinforced in sympatric populations between D. ohnishii and D. lini and between D. ohnishii and D. ogumai or that it has evolved in a very restricted local population of D. ohnishii, possibly by a few mutations.     

Search for species-specific mating signal in courtship songs of sympatric sibling species,Drosophila ananassae and D. pallidosa

Sexual isolation is one of the most important mechanisms that may lead to speciation. Drosophila ananassae and D. pallidosa are useful for the study of sexual isolation, because of their sympatric distribution and no postmating isolation between them. Courtship songs are considered to play a crucial role in sexual isolation between D. ananassae and D. pallidosa. We recorded and analyzed male courtship songs of D. ananassae and D. pallidosa for eight and four geographical strains, respectively. Courtship behaviors of the two species were consistent with those previously described, however, male's middle leg shaking, which had not before been described, was observed in both species. Males sing by wing vibration only during courtship. Their song oscillograms were distinct between species, but those of conspecific strains were very similar, in spite of their different geographical derivation. We found species-specificity in burst length, pulse length, cycle number in a pulse, and frequency spectra of bursts; these results suggest that these song parameters may play a role in mate recognition that enforces their sexual isolation. The specific values of interpulse interval, cycle number in a pulse and intrapulse frequency were involved with the determination of specificity in frequency spectra of bursts. We discussed the possibility that the specific frequency spectra of bursts are recognized by females as the species-specific signal rather than each parameter individually.     

Divergence in Multiple Courtship Song Traits between Drosophila santomea and D. yakuba

The courtship song of Drosophila is useful for species recognition and sexual selection. A new species of the melanogaster group of Drosophila , D. santomea , has recently been described from the island of São Tomé in the Gulf of Guinea. We describe the courtship song of D. santomea and compare it with that of its sibling species D. yakuba . Both species have a relatively unusual song pattern for melanogaster-group species, in that they have two types of pulse song but no sine song. There are large differences in the inter-pulse interval of both types of song, but no major differences in pulse shape or intrapulse frequency between the species. The song of D. yakuba is similar in lines from the African mainland (allopatric to D. santomea ) and from São Tomé (sympatric). We test if song pattern might influence sexual isolation by examining the mating success of wingless males with homo- and hetero-specific females. We show that song pattern contributes to sexual stimulation, but the differences in song patterns alone are unlikely to explain patterns of sexual isolation such as the asymmetrical isolation seen between species.     

Genetics of incipient speciation in Drosophila mojavensis. I. Male courtship song, mating success, and genotype x environment interactions

Few studies have examined genotype by environment (GxE) effects on premating reproductive isolation and associated behaviors, even though such effects may be common when speciation is driven by adaptation to different environments. In this study, mating success and courtship song differences among diverging populations of Drosophila mojavensis were investigated in a two-environment quantitative trait locus (QTL) analysis. Baja California and mainland Mexico populations of D. mojavensis feed and breed on different host cacti, so these host plants were used to culture F2 males to examine host-specific QTL effects and GxE interactions influencing mating success and courtship songs. Linear selection gradient analysis showed that mainland females mated with males that produced songs with significantly shorter L(long)-IPIs, burst durations, and interburst intervals. Twenty-one microsatellite loci distributed across all five major chromosomes were used to localize effects of mating success, time to copulation, and courtship song components. Male courtship success was influenced by a single detected QTL, the main effect of cactus, and four GxE interactions, whereas time to copulation was influenced by three different QTLs on the fourth chromosome. Multiple-locus restricted maximum likelihood (REML) analysis of courtship song revealed consistent effects linked with the same fourth chromosome markers that influenced time to copulation, a number of GxE interactions, and few possible cases of epistasis. GxE interactions for mate choice and song can maintain genetic variation in populations, but alter outcomes of sexual selection and isolation, so signal evolution and reproductive isolation may be slowed in diverging populations. Understanding the genetics of incipient speciation in D. mojavensis clearly depends on cactus-specific expression of traits associated with courtship behavior and sexual isolation.     

Species and sex-specific songs and courtship behaviour in the genus Zaprionus (Diptera-Drosophilidae)

Courtship behaviour and songs of six Zaprionus species show differences not only between species but also between sexes. Courtship behaviour differs from that in the related genus Drosophila. In most species, males produce two song types which may alternate or be repeated. Singing occurs during courtship displays, mounting, after copulation and briefly during male-to-male interactions. Females produce a loud whine and body rocking movements in refusal but have a species-specific pulsed song produced during normal courtship which differs from the conspecific male song. One species produces an irregular male song but a regular female song. Sex-specific songs may have selective advantages but pose problems for the sensory template hypothesis.     

Courtship song analysis of Drosophila muscle mutants

As part of the mating ritual, males of Drosophila species produce species-specific courtship songs through wing vibrations generated by the thoracic musculature. While previous studies have shown that indirect flight muscles (IFM) are neurally activated during courtship song production, the precise role of these muscles in song production has not been investigated. Fortunately, IFM mutants abound in Drosophila melanogaster and studies spanning several decades have shed light on the role of muscle proteins in IFM-powered flight. Analysis of courtship songs in these mutants offers the opportunity to uncover the role of the IFM in a behavior distinct than flight and subject to different evolutionary selection regimes. Here, we describe protocols for the recording and analysis of courtship behavior and mating song of D. melanogaster muscle transgenic and mutant strains. To record faint acoustic signal of courtship songs, an insulated mating compartment was used inside a recording device (INSECTAVOX) equipped with a modified electret microphone, a low-noise power supply, and noise filters. Songs recorded in the INSECTAVOX are digitized using Goldwave, whose several features enable extraction of critical song parameters, including carrier frequencies for pulse song and sine song. We demonstrate the utility of this approach by showing that deletion of the N-terminal region of the myosin regulatory light chain, a mutation known to decrease wing beat frequency and flight power, affects courtship song parameters.     

Courtship inDrosophila sechellia: Its structure,functional aspects,and relationship to those of other members of theDrosophila melanogaster species subgroup

The courtship behavior of Drosophila sechelliais described. Male wing displays are mainly vibration and scissoring, with low levels of rowing. As courtship proceeds the proportion of courtship spent in male wing vibration and licking increases, whereas female movement decreases. The male courtship song of sechelliacontains pulse song but no sine song. This species also shows a distinctive copulation song associated with mounting and copulation. The main cuticular hydrocarbon in females is 7,11-heptacosadiene. The number of copulations increased when flies were placed in the presence of food. Visual and acoustic stimuli appear to be important for mating. A multidimensional comparison was used to compare members of the melanogaster species subgroup, based upon courtship behavior, song characteristics, and cuticular hydrocarbons. A multidimensional comparison of courtship sequences in sechellia, melanogaster, simulans,and mauritianashowed differences in variability between the two island species as compared to the two cosmopolitan species. The courtship song of D. orenais described: it shows both sine and pulse song; there is also a copulation song in this species.     

Genetics of sexual isolation based on courtship song between two sympatric species: Drosophila ananassae and D. pallidosa

Sexual isolation has been considered one of the primary causes of speciation and its genetic study has the potential to reveal the genetics of speciation. In Drosophila, the importance of courtship songs in sexual isolation between closely related species has been well investigated, but studies analysing the genetic basis of the difference in the courtship songs associated with sexual isolation are less well documented. Drosophila ananassae and Drosophila pallidosa are useful for studies of sexual isolation, because of their sympatric distribution and absence of postmating isolation. Courtship songs are known to play a crucial role in sexual isolation between these two species, and the female discrimination behaviour against the courting male has been revealed to be controlled by a very narrow region on the second chromosome. In this study we investigated the genetic basis controlling the song differences associated with their sexual isolation, using intact and wingless males with chromosomes substituted between species. The results obtained from F₁ hybrid males between these species indicate the dominance of the song characters favoured by D. pallidosa females. In addition, the results obtained from backcross F₂ males indicate that chromosome 2 had a major effect on the control of the song characters associated with sexual isolation.     

Song production in auditory mutants of Drosophila: the role of sensory feedback

To test the role of sensory feedback in song production. we analyzed the courtship songs of Drosophila males expressing auditory mutations. We compared the courtship songs of atonal (ato), beethoven (btv) and touch-insensitive-larva-B (tilB) to wild-type songs. These mutations have in common the fact that the chordotonal organs are disrupted. Since chordotonal organs subserve both hearing (in the antenna) and proprioception (from the wing), these two potential routes for sensory feedback are defective in the mutant flies. We measured six song characters: pulse number within a train, inter-pulse interval, pulse duration, sine burst duration, the carrier frequency of the sine song and the relative amplitude of the sine song. Using multivariate analysis, we found significant differences between mutant and normal songs. In addition many mutant flies exhibit an unusual wing position during singing. The results indicate that sensory feedback plays an important role in shaping the courtship song of Drosophila.     

Behavioral Sequence Leading to Sexual Isolation Between <Emphasis Type="Italic">Drosophila ananassae</Emphasis> and <Emphasis Type="Italic">D. pallidosa</Emphasis>

Drosophila ananassae and D. pallidosa are closely related, sympatric species that lack postmating isolation. Sexual isolation has been considered important in maintaining them as independent species. To clarify the behavioral processes leading to sexual isolation, we analyzed behavioral sequences and examined the effect of courtship song on mating success and on behaviors of both sexes by surgically removing male wings (song generators), female aristae (song receivers), or female wings (means of fluttering). We found that heterospecific courtship songs evoked female wing fluttering, whereas conspecific courtship song did not. Furthermore, female wing fluttering made courting males discontinue courtship. These findings suggest that strong sexual isolation is achieved through the following behavioral sequence: heterospecific song→female wing fluttering→courtship discontinuation.     

Courtship song recognition in the Drosophila melanogaster complex: heterospecific songs make females receptive in D. melanogaster, but not in D. sechellia

Abstract. The courtship song emitted by male wing vibration has been regarded as one of the most important signals in sexual isolation in the species of the Drosophila melanogaster complex. Inter- and intraspecific crosses were observed using males whose wings were removed (mute) or females whose aristae were removed (deaf). Females of D. melanogaster, D. simulans , and D. mauritiana mated with heterospecific males in the song-present condition (cross between normal females and winged males) more often than in the no-song condition (cross between normal females and wingless males or between aristaless females and winged males) or they showed no preference between the two conditions. It is possible that in these females heterospecific courtship songs play a role as if they were conspecific. In contrast, the females of D. sechellia mated with D. melanogaster or D. simulans males in the no-song condition more often than in the song-present condition, suggesting that they reject males with heterospecific song. Female mate recognition depending on the courtship song in D. melanogaster, D. simulans , and D. mauritiana is considered to be relatively broader and that in D. sechellia narrower.     

Female mate recognition and sexual isolation depending on courtship song in Drosophila sechellia and its siblings

In Drosophila sechellia, females accept males that sing heterospecific songs less than those that do not sing, whereas in D. melanogaster and D. simulans, females accept males that sing heterospecific song more than those that do not sing. Here we studied the sexual isolation of D. sechellia and its siblings using interspecific hybrids to reveal the mechanisms underlying female mate recognition. The females of hybrids mated more with winged males of the parent species than with wingless ones, suggesting that the discrimination against heterospecific songs by D. sechellia females is recessive. Female preference for courtship songs seems to be inherited additively or semidominantly. In addition, we examined female receptivity without the stimuli of courtship songs by comparing the mating frequencies between the crosses using wingless males and found that it is also inherited additively or semidominantly.     

The structure and function of songs emitted by southern green stink bugs from Brazil, Florida, Italy and Slovenia

Nezara viridula (L.) (Pentatomidae: Heteroptera) from Brazil, Florida, Italy and Slovenia, communicate by vibratory songs associated with long‐range calling and close‐range courting, rivalry and repelling. Each song is composed of spectrally and temporally different units. Spectrally different pulses of duration less than 300 ms are present in the male calling song. The female calling song is characterized by pulse trains composed of pulses shorter than 150 ms and pulse trains composed of a longer (> 700 ms) and shorter (< 250 ms) pulse. Shorter and longer pulses have different spectral characteristics. The male and female courtship songs are characterized by fusion of shorter (< 150 ms) pulses into a pulse train usually followed by a shorter (< 200 ms) postpulse in the case of the male courtship song. The female repelling song is a several seconds long vibration of irregular temporal structure. The short (< 400 ms) male rival song pulses are frequency modulated. The dominant frequency peaks of the songs investigated lie between 70 and 130 Hz. The dominant frequency and the microstructure of song spectra show no population specificity. The average duration varies more in calling than in courtship songs. The repetition time varies extensively in songs of different populations. Normal communication followed by copulation was observed between mates from Slovenia and Brazil and between mates from Florida and Italy. The potential role of different temporal and spectral parameters for species recognition and mate location is discussed in view of the expected distortion of the characteristic signal structure during transmission through plants.     

Courtship-sounds and behaviour in the four species of the Drosophila bipectinata complex

The D. bipectinata complex contains four species which are sympatric over parts of their range. They are morphologically identical and hybridize in no-choice mating situations. They have similar but distinct courtship patterns and males of all species sing two songs, long song early and short song late in courtship. Each species has a unique song profile due to differences in at least one song parameter. This is circumstantial evidence that sounds function to maintain sexual isolation within the complex.     

黑腹果蝇野生型和翅形眼色异常突变型的求爱歌的比较研究

黑腹果蝇(D.melanogaster)雄蝇发出的求爱歌系由两个不同的成分——正弦歌和脉冲歌组成。正弦歌在刺激雌蝇发情上可能起着重要的作用,而脉冲歌则关系到种的识别。 在脉冲歌的诸成分中,脉冲间间隔(ipi)特别重要。我们对野生型和突变型SM_1Cy/Pm,SM_1Cy/+和+/Pm进行了研究。虽然突变型有异常的翅形和异常的眼色,但实验结果表明,野生型和上述突变型的ipi平均值是一致的。     

Courtship signals and mate choice of the flies of inbred Drosophila montana strains

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.     

Song Choice Is Modulated by Female Movement in Drosophila Males

Mate selection is critical to ensuring the survival of a species. In the fruit fly, Drosophila melanogaster, genetic and anatomical studies have focused on mate recognition and courtship initiation for decades. This model system has proven to be highly amenable for the study of neural systems controlling the decision making process. However, much less is known about how courtship quality is regulated in a temporally dynamic manner in males and how a female assesses male performance as she makes her decision of whether to accept copulation. Here, we report that the courting male dynamically adjusts the relative proportions of the song components, pulse song or sine song, by assessing female locomotion. Male flies deficient for olfaction failed to perform the locomotion-dependent song modulation, indicating that olfactory cues provide essential information regarding proximity to the target female. Olfactory mutant males also showed lower copulation success when paired with wild-type females, suggesting that the male’s ability to temporally control song significantly affects female mating receptivity. These results depict the consecutive inter-sex behavioral decisions, in which a male smells the close proximity of a female as an indication of her increased receptivity and accordingly coordinates his song choice, which then enhances the probability of his successful copulation.     

Courtship songs and genetic control of their acoustic characteristics in sibling species of the Drosophila melanogaster subgroup

Six sibling species of the melanogaster subgroup differ in their wing displays and in the acoustic characteristics of their courtship songs. D. melanogaster, D. simulans and D. mauritiana have distinct but similar courtship songs. D. mauritiana, which is allopatric to the others, produces, an ambivalent song with sine song frequency and intrapulse frequency like simulans and modal interpulse interval like melanogaster. These three species appear to be behaviourally more closely similar to each other than to the three African species D. yakuba, D. teissieri and D. erecta. The acoustic characteristics of the songs of interspecific hybrids, indicate that the interpulse interval and intrapulse frequency are quantitatively controlled by genes located on the autosomes. The ability to generate sine song may be controlled by one or more genes located on the X-chromosome, but an alternative possibility, of autosomal dominant inheritance, cannot be excluded.     

Sexual selection,sexual isolation and the evolution of song in the Drosophila repleta group of species

The evolution of male courtship song pattern in fruit flies of the repleta group within the genus Drosophila is described. We suggest that the archetypal song was composed of two distinct components, an ‘A’ song with short, regular pulse trains which occurred at the beginning of courtship, and a ‘B’ song consisting of longer pulse trains of more widely spaced pulses occurring later in courtship. During evolution of the repleta group some species have lost the A song, others the B song and, in many species, the latter has become less regular and more complex in form. A songs appear to be involved primarily in species recognition and have been subject to stabilizing selection while the B songs sexually stimulate females and have therefore evolved rapidly through the action of sexual selection. Other factors influencing the evolution of song patterns have been certain physiological and energetic constraints.     

Rapid evolution of courtship song pattern in Drosophila willistoni sibling species

Courtship behaviours may provide a more reliable means of identifying reproductively isolated taxa than traits such as morphology or many genetic markers. Here we describe the courtship songs of the Drosophila willistoni sibling species group, which consists of several species and subspecies. We find that song pattern is species-specific, despite significant differences among strains within species. D. paulistorum has the most variable song pattern, which reflects this species' traditional subdivision into semispecies. All the other species could be unambiguously identified by song. The major differences among these species was in the interpulse interval, as has been found in other studies of fly song. However, the interpulse intervals of the species studied here were often multimodal. This was partly due to the presence of multiple song types within the courtship repertoire, but it also reflected changes in interpulse interval within a song type by some males. Unusually, some species had distinctively patterned variation in interpulse interval. Song must have evolved rapidly within the species complex, probably due to sexual selection.