53 research outputs found
Wings and bristles: character specificity of the asymmetry phenotype in insecticide-resistant strains of Lucilia cuprina
Temperature shock during development fails to increase the fluctuating asymmetry of a sexual trait in stalk-eyed flies.
The fluctuating asymmetry (FA) of bilateral traits is claimed to be a general indicator of environmental stress. Exaggerated sexual ornaments are thought to show elevated levels of FA and a greater response to stress than other traits. Previous work with stalk-eyed flies (Cyrtodiopsis dalmanni) has shown that the FA of the sexual trait (male eye stalks), wing length and wing width were unaffected by a continually applied food stress. Here we tested whether a transient stress (24-h heat shock at 31 degrees C during development) affected the FA of these traits. A second experiment tested the combined stresses of transient heat shock at 31 degrees C with continuous exposure to desiccation. In each experiment, temperature shock reduced the trait size, confirming that the treatments were stressful. However, stress had no effect on the FA of individual traits or the FA summed across all traits. Exposure to the combined stresses significantly elevated mortality and reduced trait size compared to the single-stress regime. However, FA did not differ significantly between flies from the two experiments. We found no evidence that FA in sexual and non-sexual traits reflects transient stress during the development of C. dalmanni
Reaction norms of size characters in relation to growth temperature in Drosophila melanogaster: an isofemale lines analysis
Reaction norms of size characters in relation to growth temperature in Drosophila melanogaster: an isofemale lines analysis
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
Reaction norms of size characters in relation to growth temperature in Drosophila melanogaster
Comparative analysis of morphological traits among <i>Drosophila melanogaster</i> and <i>D. simulans</i>: genetic variability clines and phenotypic plasticity
Seasonal stress drives predictable changes in inbreeding depression in field-tested captive populations of Drosophila melanogaster
Variations in morphological and life-history traits under extreme temperatures in Drosophila ananassae
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