Plasticity of Drosophila melanogaster wing morphology: effects of sex, temperature and density

In this paper we use an adjusted ellipse to the contour of the wings of Drosophila as an experimental model to study phenotypic plasticity. The geometric properties of the ellipse describe the wing morphology. Size is the geometric mean of its two radii; shape is the ratio between them; and, the positions of the apexes of the longitudinal veins are determined by their angular distances to the major axis of the ellipse. Flies of an inbred laboratory strain of Drosophila melanogaster raised at two temperatures (16.5°C and 25°C) and two densities (10 and 100 larvae per vial) were used. One wing of at least 40 animals of each sex and environmental condition were analyzed (total = 380), a measurement of thorax length was also taken. Wing size variation could be approximately divided into two components: one related to shape variation and the other shape independent. The latter was influenced primarily by temperature, while the former was related to sex and density. A general pattern could be identified for the shape dependent variation: when wings become larger they become longer and the second, fourth and fifth longitudinal veins get closer to the tip of the wing.