Incipient speciation in Drosophila melanogaster involves chemical signals.

The sensory and genetic bases of incipient speciation between strains of Drosophila melanogaster from Zimbabwe and those from elsewhere are unknown. We studied mating behaviour between eight strains – six from Zimbabwe, together with two cosmopolitan strains. The Zimbabwe strains showed significant sexual isolation when paired with cosmopolitan males, due to Zimbabwe females discriminating against these males. Our results show that flies' cuticular hydrocarbons (CHs) were involved in this sexual isolation, but that visual and acoustic signals were not. The mating frequency of Zimbabwe females was highly significantly negatively correlated with the male's relative amount of 7-tricosene (%7-T), while the mating of cosmopolitan females was positively correlated with %7-T. Variation in transcription levels of two hydrocarbon-determining genes, desat1 and desat2, did not correlate with the observed mating patterns. Our study represents a step forward in our understanding of the sensory processes involved in this classic case of incipient speciation

A glial amino-acid transporter controls synapse strength and courtship in Drosophila

Mate choice is an evolutionarily critical decision that requires the detection of multiple sex-specific signals followed by central integration of these signals to direct appropriate behavior. The mechanisms controlling mate choice remain poorly understood. Here, we show that the glial amino-acid transporter genderblind controls whether Drosophila melanogaster males will attempt to mate with other males. Genderblind (gb) mutant males showed no alteration in heterosexual courtship or copulation, but were attracted to normally unappealing male species-specific chemosensory cues. As a result, genderblind mutant males courted and attempted to copulate with other Drosophila males. This homosexual behavior could be induced within hours using inducible RNAi, suggesting that genderblind controls nervous system function rather than its development. Consistent with this, and indicating that glial genderblind regulates ambient extracellular glutamate to suppress glutamatergic synapse strength in vivo, homosexual behavior could be turned on and off by altering glutamatergic transmission pharmacologically and/or genetically

Electrophysiological data

Excel file containing raw electrophysiological responses from identified OSNs in response to identified odours

Behavioural elements and sensory cues involved in sexual isolation between Drosophila melanogaster strains

Sensory cues exchanged during courtship are crucial for mate choice: if they show intraspecific divergence, this may cause or reinforce sexual isolation between strains, ultimately leading to speciation. There is a strong asymmetric sexual isolation between Drosophila melanogaster females from Zimbabwe (Z) and males from all other populations (M). While M and Z flies of both sexes show different cuticular pheromones, this variation is only partly responsible for the intraspecific isolation effect. Male acoustic signals are also partly involved in sexual isolation. We examined strain-specific courtship behaviour sequences to determine which body parts and sensory appendages may be involved in sexual isolation. Using two strains representative of the Z-and M-types, we manipulated sensory cues and the social context; we then measured the consequence of these manipulations on courtship and copulation. Our data suggest that Z females mated best with males whose sensory characteristics matched those of Z males in both quantity and quality. M females were less choosy and much less influenced by the sensory and social contexts. Differences in emission and reception of sensory signals seen between Z and M flies may lead to the concerted evolution of multiple sensory channel, thereby shaping a population-specific mate recognition system

Data from: Behavioral elements and sensory cues involved in sexual isolation between Drosophila melanogaster strains

Sensory cues exchanged during courtship are crucial for mate choice: if they show intraspecific divergence this may cause or reinforce sexual isolation between strains, ultimately leading to speciation. There is a strong asymmetric sexual isolation between Drosophila melanogaster females from Zimbabwe (Z) and males from all other populations (M). While M and Z flies of both sexes show different cuticular pheromones, this variation is only partly responsible for the intraspecific isolation effect. Male acoustic signals are also partly involved in sexual isolation. We examined strain-specific courtship behaviour sequences to determine which body parts and sensory appendages may be involved in sexual isolation. Using two strains representative of the Z- and M-types, we manipulated sensory cues and the social context; we then measured the consequence of these manipulations on courtship and copulation. Our data suggest that Z females mated best with males whose sensory characteristics matched those of Z males in both quantity and quality. M females were less choosy and much less influenced by the sensory and social contexts. Differences in emission and reception of sensory signals seen between Z and M flies may lead to the concerted evolution of multiple sensory channel, thereby shaping a population-specific mate recognition system

Implication des signaux sensoriels dans la réceptivité sexuelle de la femelle Drosophila mélanogaster (cas d'isolement reproducteur chez des populations du Zimbabwe)

La parade sexuelle de la mouche Drosophila melanogaster consiste en un échange de signaux sensoriels entre le mâle et la femelle, échange qui aboutit ou non à l accouplement. Ces signaux sont de natures diverses : visuelles, acoustiques, chimiques. Bien que le comportement sexuel du mâle a largement été étudié, celui de la femelle reste encore mal documenté. Lors de ma thèse, j ai étudié l'influence des signaux du mâle sur la réceptivité sexuelle des femelles D. melanogaster en m'intéressant au cas de l isolement reproducteur asymétrique existant entre les lignées endémiques du Zimbabwe et les lignées Cosmopolites : les femelles du Zimbabwe montrent une propension réduite à s accoupler avec les mâles Cosmopolites. Ainsi en comparant le comportement des femelles Zimbabwe et des femelles Cosmopolites envers un même mâle, il est possible de déterminer quels signaux sensoriels peuvent influencer la réceptivité des premières et être impliqués dans l isolement reproducteur. Dans un premier temps, j ai confirmé l existence d un isolement reproducteur entre les lignées Zimbabwe et Cosmopolites et montré qu il existait même un isolement reproducteur entre certaines lignées du Zimbabwe. Dans un second temps, j ai tenté de modifier un à un les signaux sensoriels des mâles et observé l impact de cette modification sur la propension à s'accoupler de la femelle. Ainsi, pour étudier l implication des signaux visuels, j ai réalisé des expériences en lumière rouge et en lumière blanche et occulté la vision d un ou des deux partenaires sexuels grâce à l utilisation d un vernis opaque. L étude de l implication des signaux chimiques a été réalisée à l aide de transfert d hydrocarbures cuticulaires chez les mâles mais aussi chez les femelles (des lignées étudiées ou de la lignée mutante 1573 qui ne produit pas de phéromones sexuelles), ainsi qu à l aide d ablations des structures réceptrices des signaux chimiques chez les mâles et les femelles. Enfin, différentes ablations alaires et des expériences de rediffusion du chant des mâles m ont permis d examiner l implication des signaux acoustiques dans l isolement reproducteur entre les lignées Zimbabwe et les lignées Cosmopolites. Il ressort de mes recherches que la communication sexuelle entre les mâles et les femelles drosophiles est complexe et fait intervenir plusieurs signaux sensoriels. De plus, cette communication n est pas stéréotypée et varie en fonction des génotypes des partenaires. Et enfin, même s il a été possible de démontrer un refus des femelles Zimbabwe de s accoupler avec les mâles Cosmopolites, il n a pas été possible de comprendre tous les mécanismes impliqués dans l isolement reproducteur entre les femelles endémiques du Zimbabwe et les mâles Cosmopolites.Sexual courtship in Drosophila melanogaster consists of an exchange of sensory signals between both mates which results in successful copulation or not. These signals are various in nature: visual, acoustic, chemical. While male sexual courtship was already well studied, the female sex behaviour still remains poorly documented. In my Ph.D. thesis, I studied the role of male signals on the female sexual receptivity in D. melanogaster, focusing my research on the case of asymmetrical sexual isolation which occurs between endemic Zimbabwe strains and cosmopolitan ones: Zimbabwe females have a reduced propensity to mate with cosmopolitan males. Comparying the behaviour of endemic and cosmopolitan females toward a single male allows to determine which sensory signals could influence the female receptivity and, therefore, be involved in sexual isolation. First, I confirmed the sexual isolation occuring between Zimbabwe and cosmopolitan strains, and showed that such a sexual isolation even occurs between some endemic Zimbabwe strains. Secondly, to evaluate their role in the female propensity to mate, I have individually modified the sensory signals emitted by the male by using red light instead of white one, occulting sex partners eyes with opaque varnish, by transferring cuticular hydrocarbons between flies from various lines, by ablating wings. Finally, experiments of playback emission allowed me to envisage the involvement of male love songs in the isolation mechanisms between Zimbabwe and cosmopolitan Drosophila lines. From this work, it appears that in fruit flies the "sexual communication" between mates is a very complicated process involving all the sensory modalities. Furthermore, it is not stereotyped and varies according to the partner genotype. Even if I proved the existence of an asymmetrical sexual isolation between Zimbabwe and cosmopolitan Drosophila, all the mechanisms underlying this isolation are not yet fully understood.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Behavioural elements and sensory cues involved in sexual isolation between Drosophila melanogaster strains

International audienceSensory cues exchanged during courtship are crucial for mate choice: if they show intraspecific divergence, this may cause or reinforce sexual isolation between strains, ultimately leading to speciation. There is a strong asymmetric sexual isolation between Drosophila melanogaster females from Zimbabwe (Z) and males from all other populations (M). While M and Z flies of both sexes show different cuticular pheromones, this variation is only partly responsible for the intraspecific isolation effect. Male acoustic signals are also partly involved in sexual isolation. We examined strain-specific courtship behaviour sequences to determine which body parts and sensory appendages may be involved in sexual isolation. Using two strains representative of the Z-and M-types, we manipulated sensory cues and the social context; we then measured the consequence of these manipulations on courtship and copulation. Our data suggest that Z females mated best with males whose sensory characteristics matched those of Z males in both quantity and quality. M females were less choosy and much less influenced by the sensory and social contexts. Differences in emission and reception of sensory signals seen between Z and M flies may lead to the concerted evolution of multiple sensory channel, thereby shaping a population-specific mate recognition system

Chemically mediated sexual isolation between Zimbabwean endemic and cosmopolitan populations of Drosophila melanogaster

Chemically mediated sexual isolation between Zimbabwean endemic and cosmopolitan populations of [i]Drosophila melanogaster[/i]. ISCE 26. annual meetin

Data from: The peripheral olfactory code in Drosophila larvae contains temporal information and is robust over multiple timescales

We studied the electrophysiological activity of two classes of Drosophila melanogaster larval olfactory sensory neurons (OSNs), Or24a and Or74a, in response to 1 s stimulation with butanol, octanol, 2-heptanone, and propyl acetate. Each odour/OSN combination produced unique responses in terms of spike count and temporal profile. We used a classifier algorithm to explore the information content of OSN activity, and showed that as well as spike count, the activity of these OSNs included temporal information that enabled the classifier to accurately identify odours. The responses of OSNs during continuous odour exposure (5 and 20 min) showed that both types of neuron continued to respond, with no complete adaptation, and with no change to their ability to encode temporal information. Finally, we exposed larvae to octanol for 3 days and found only minor quantitative changes in OSN response to odours, indicating that the larval peripheral code is robust when faced with long-term exposure to odours, such as would be found in a natural context