Developmental constraints and wing shape variation in natural populations of Drosophila melanogaster

Abstract

The body sizes and shapes of poikilothermic animals generally show clinal variation with latitude. Among the environmental factors responsible for the dine, temperature seems to be the most probable candidate. In the present work we analysed natural populations of Drosophila melanogaster collected at different geographical localities to determine whether the same selective forces acting on wing development in the laboratory are also at work in the wild. We show that the temperature selection acting on wing development in the laboratory is only one of the selective forces operating in the wild. The size differences between natural populations seem to depend exclusively on cell number whereas they depend on cell area in the laboratory. The two wing compartments behave as distinct units of selection subjected to different genetic control, confirming our previous observations on laboratory populations. In addition, subunits of development defined as regions of cell proliferation centres restricted within longitudinal veins can, in turn, be considered as subunits of selection. Their interaction during development and continuous natural selection around an optimum could explain the high wing shape stability generally found in natural populations.

Different Cell Size and Cell Number Contribution in Two Newly Established and One Ancient Body Size Cline of Drosophila Subobscura

“…Cell density varies across the surface of the Drosophila wing. However, concordant differences in the cell area between different parts of the wing blade are found for differences between both individuals and populations (see Delcour and Lints 1966;Partridge et al 1994;Pezzoli et al 1997). The proximal and distal part of vein IV showed a different lengthening pattern with latitude in the European and North American clines (Huey et al 2000;Gilchrist et al 2001).…”

“…Several studies (e.g., Robertson 1959;Cavicchi et al 1985;Partridge et al 1994) have found that laboratory thermal selection lines differ in wing area entirely as a consequence of a difference in cell size. Latitudinal clines, on the other hand, show variation in wing area based mainly on cell number, with cell size contributing at most only a small amount (James et al 1995(James et al , 1997Pezzoli et al 1997;Zwaan et al 2000).…”

Geographic Variation for Wing Shape in Drosophila Serrata

“…The first principal component is taken to represent size and the other components are the shape dimensions. Measurements of angles between wing axes have also been used as shape measures (Weber et al 1999), as have the relative sizes of wing compartments (Pezzoli et al 1997) and the relative length of a wing compared to its width/ area, referred to as wing aspect (Azevedo et al 1998). Another approach is to superimpose an ellipse on a wing when estimating shape (Bitner-Mathe and Klaczko 1999a).…”

“…They found changes in the ratio of proximal-distal sections of the posterior wing and suggested that these changes reflected selection due to mean temperature, as high temperatures in the laboratory lead to the elongation of the distal parts of the wing and widening of the posterior compartment. Pezzoli et al (1997) collected D. melanogaster from four localities and characterized variation in compartments of the wings. They showed that not all compartments change equally with overall size, resulting in shape differences among the locations.…”

Wing morphology of the active flyerCalliphora vicina(Diptera: Calliphoridae) during its invasion of a sub-Antarctic archipelago where insect flightlessness is the rule

“…Noticeable differences in the anterior-proximal region of the wing were found between females from the two populations of C. vicina, thereby supporting our second hypothesis that pressures on flight morphologies may differ between the two geographical areas. We only found limited allochronic change in the anterior-proximal region of the wing, but it is usually less variable than the posterior-distal region (see results in Pezzoli et al, 1997;Gilchrist et al, 2000), arguably because of the aforementioned functional constraints. Additional studies will be necessary to test whether the differences in the leading edge between the two populations resulted from the introduction of C. vicina in the Kerguelen Islands before our first sample or pre-existed in the population of origin.…”