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Title: Thermal evolution of body size in Drosophila melanogaster
Author: Azevedo, Ricardo Bruno Rebelo de
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1997
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The objective of this research was to investigate the causes and consequences of thermal evolution of body size in Drosophila melanogaster. This was done empirically by the integrated study of lines collected along latitudinal gradient and population that were undergoing long-term evolution at different temperatures in the laboratory. All experiments were conducted in the laboratory using controlled conditions of temperature and larval density. I examined 20 populations collected along a north-south transect in Australia (17°-43°S) and found that wing size increased with latitude. The genetic cline in wing size was mostly based on variation in cell number (82%). These findings contradicted previous results on thermal selection in the laboratory, where the divergence in wing size was achieved almost entirely by changes in cell size. In another experiment, 6 geographic lines were reared at 5 temperatures spanning the entire viability range for the species. Wing size, cell size and cell number all decreased with increasing development temperature. Cell size determined most of the plasticity in wing size (˜75%). Wing size increased with latitude across the reaction norm, mostly due to variation in cell number (87%), which repeated the pattern observed at a single temperature. Although there was significant variation among populations in phenotypic plasticity of the wing traits, a latitudinal trend in this variation was only detected for cell size; variation in plasticity of wing size among populations was attributable to both cellular components. The results of these experiments suggest that thermal evolution acted on body size itself, since cell number is the basis of additive genetic variation for body size within populations at a single temperature. In the experiments outlined above, it was also found that the size of the wing, relative to the size of the thorax, and the relative length of the wing both decreased in response to high selection and developmental temperatures.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available