Search

Two species of Drosophilid are added to the French fauna., Deux espèces de Drosophiles sont rajoutées à la faune française., Withers Philippe. Deux espèces d'Amiota du sous-genre Phorttca nouvelles pour la France (Diptera Drosophilidae). In: Bulletin mensuel de la Société linnéenne de Lyon, 63ᵉ année, n°6, juin 1994. p. 224.

Ten isofemale lines of Drosophila melanogaster, recently collected in a French vineyard, were submitted to 7 different developmental temperatures, from 12 to 31°C, encompassing the whole physiological range of the species. For each line and temperature, 10 flies of each sex were collected randomly and 2 size-related traits were measured: wing and thorax length. Both traits exhibited similar response curves: a maximum size at a low temperature and a decrease on both sides. ANOVA showed significant variations between lines and also significant line-temperature interactions, demonstrating different norms of reaction among the various lines. The shapes of the curves were further analysed by considering slope variations, ie by calculating empirical derivative curves. The most interesting observation is that the temperature of maximum size (TMS) is not the same for the wing (average 15.73 ± 0.29°C) and the thorax (average 19.57 ± 0.47°C). Genetic differences seem to exist between lines, and TMS for both traits are correlated. Sexual dimorphism was analysed by considering the female/male ratio for wing and thorax. Both traits provided the same information: sexual dimorphism increased, from 1.10 to 1.16, with increasing temperature, and significant differences were found between lines. Finally the wing/thorax ratio appeared as an original and most interesting trait. This ratio, which is less variable than wing or thorax, exhibited a monotonously decreasing sigmoid shape, from 2.80 to 2.40, with increasing temperature. It is suggested that this ratio, which may be related to flight capacity at various temperatures, could be the direct target of natural selection., Dix lignées isofemelles de Drosophila melanogaster, récemment récoltées dans un vignoble français du sud-ouest de la France, ont été soumises à 7 températures différentes (de 12 à 31°C) compatibles avec le développement de l’espèce. Pour chaque Lignée et chaque température, 10 mouches de chaque sexe ont été choisies au hasard. Sur chaque individu, 2 caractères relatifs à la taille ont été mesurés : la longueur de l’aile et la longueur du thorax. Les courbes de réponse des 2 caractères ont la même forme et mettent en évidence une taille maximum en dessous de 20°C et une décroissance de part et d’autre de ce maximum. Des variations significatives entre les lignées de même que des interactions significatives lignée-température sont mises en évidence par ANOVA, ce qui montre que les normes de réaction des différentes lignées ont des formes différentes. L’analyse de la forme des courbes a été réalisée en considérant les variations des pentes pour chaque intervalle de température, c’est-à-dire en calculant empiriquement une dérivée. L’observation la plus remarquable concerne la température pour laquelle la taille est maximale: 15, 73 ± 0, 29°C pour l’aile et 19, 57 ± 0, 47°C pour le thorax. Des différences génétiques entre les lignées sont mises en évidence pour cette température de taille maximum, et les valeurs obtenues pour les 2 caractères sont corrélées. Le rapport femelle-mâle pour l’aile ou le thorax permet d’étudier le dimorphisme sexuel. Le rapport augmente de 1,10 à 1,16 quand la température passe de 12 à 31° C. Il existe aussi des différences significatives entre les Lignées. Il est montré que le rapport aile-thorax est un critère original et d’un grand intérêt. Ce rapport est relativement moins variable que l’aile ou le thorax. Il décroît selon une sigmoïde à mesure que la température augmente et varie de 2,80 à 2,40. Vraisemblablement en relation avec la capacité de vol en fonction de la température, le rapport aile-thorax pourrait être la cible directe de la sélection naturelle.

International audience

Summary - Nine Indian geographical populations of Drosophila melanogaster, collected along the 20°N latitudinal range, revealed a significant clinal variation at the alcohol dehydrogenase (Adh) locus, Adh allelic frequency increasing significantly with latitude (0.036 ! 0.004 for 1° latitude; genetic divergence F = 0.25). Patterns of ethanol and acetic-acid tolerance in adult individuals revealed significant genetic divergence. Parallel patterns of latitudinal ethanol tolerance (10 to 15%) and acetic-acid tolerance (3.7 to 13.2%) were observed in adult individuals from the 9 geographical populations. Thus, the northern and southern populations revealed divergence in the patterns of resource utilisation. The parallel latitudinal genetic divergence at the Adh locus and for ethanol and acetic-acid tolerance in Indian populations of Drosophila melanogaster could be explained by balancing natural selection varying spatially along the north-south axis of the Indian subcontinent. ADH polymorphism / ethanol tolerance / acetic-acid tolerance / latitudinal clines / Indian populations / Drosophila melanogaster

International audience

International audience

International audience

Summary — In natural populations of Drosophila melanogaster throughout the world a minority of flies are infected by a rhabdovirus, sigma, which is not contagious but is transmitted through gametes. Transmission of the virus by males is a cornerstone for its maintenance in populations. The experiments reported in this paper show that in the wild European populations examined the efficiency of transmission by males is determined mainly by viral genotype. In African populations, genetic coadaptation of both partners can lead to a very low transmission of the virus by males. Evidence is also given of the coexistence in populations of different genotypes of the virus. The situation reported is thus another example of the genetic polymorphism displayed by the sigma virus in the wild.

International audience

International audience

International audience

International audience

for the Adh locus in D. hydei in Hungary. The number of species was lower in distilleries than outside. The heterozygosity level in samples from distilleries was generally lower than in samples from outside. This result gives support to the hypothesis that the more diverse the environment the higher the level of polymorphism maintained.

Summary - Minority-male mating advantage is a phenomenon whereby genetic variability can be maintained in populations without genetic load at equilibrium. Rare-male mating advantage has been shown to be a widespread phenomenon in Drosophila, although it is seen to be absent in some species. During the present investigation, experiments were conducted to study the mating success of wild type and mutant males at different ratios in the Elens-Wattiaux mating chamber using sepia and cardinal mutant stocks and a wildtype stock in order to detect a rare male effect in D. ananassae. In all the experiments the female-choice technique was employed. Red eye males were tested separately with sepia and cardinal mutants. Experiments were conducted at 9 different ratios. The results show that although both types of males are equally successful in mating when present in the same ratio, they are more successful in mating when in a minority. This advantage disappears when the males become common. Thus the present results provide evidence for the existence of a minority-male mating advantage in D. ananassae. Drosophila ananassae - sepia and cardinal mutants - rare male mating advantage

International audience

The D. simulans SimES strain is characterized by the presence of individuals of S phenotype (malformation and/or suppression of thoracic bristles, mainly the dorsocentral and scutellar ones), with a variable frequency ranging approximately from 50 p. 100 to 60 p. 100. Since this phenotype is transmitted maternally, the presence of a microorganism responsible for that phenotype can be suspected. The presence of 2 pathogenic microorganisms in the SimES strain, a microsporidia (Nosema kingi) and a Picornavirus (Dro.sophila C virus) was detected. In flies free of both microorganisms, the S phenotype maintains the same properties, and therefore, it can be concluded that they play no part in the S phenotype determination. However, several experimental results, i.e. effects of temperature, infectious action of SimES extracts, and no effect of antibiotics, have led us to formulate the hypothesis that S phenotype is due to action of slightly pathogenic virus transovarially transmitted., La souche SimES de Drosophila simulans se caractérise par la présence d’individus de phénotype S [malformations et (ou) suppression de soies thoraciques, principalement des dorso-centrales et des scutellaires], avec une fréquence de 50 à 60 p. 100. Ce phénotype est transmis maternellement, rendant donc plausible a priori le rôle de micro-organismes dans son déterminisme. De fait, 2 micro-organismes pathogènes ont été trouvés dans la souche SimES, la microsporidie Nosema kingi et un Picornavirus, le virus C de la Drosophile. Dans les mouches débarrassées de ces 2 micro-organismes, le phénotype S se maintient avec les mêmes propriétés. Ces 2 agents ne jouent donc aucun rôle dans le déterminisme de ce phénomène. Cependant, certains résultats expérimentaux (effets de la température, pouvoir infectieux des extraits de drosophiles SimES, absence d’action d’antibiotiques) conduisent à formuler l’hypothèse que le phénotype S est dû à l’action d’un virus légèrement pathogène, à transmission transovarienne.

International audience

Tsacas Léonidas, David Jean. Drosophila mauritiana n. sp. du groupe melanogaster de l'Ile Maurice [Dipt. Drosophilidae]. In: Bulletin de la Société entomologique de France, volume 79 (1-2), Janvier-février 1974. pp. 42-46.