Genetic and environmental canalization are not associated among altitudinally varying populations ofDrosophila melanogaster

Abstract

14Organisms are exposed to environmental and mutational effects influencing both mean and 15 variance of phenotypes. These potentially deleterious effects can be ameliorated by the 16 evolution of buffering (canalizing) mechanisms, resulting in reduced phenotypic variation. 17Under some population genetics models, the circumstances under which genetic canalization 18 evolves is limited. As such, it has been argued that canalizing mechanisms for environmental 19 and mutational stresses may co-evolve, and will be correlated. Yet, empirical evidence has 20 not consistently supported this prediction. In a recent study, a population of Drosophila 21 melanogaster adapted to high altitude showed evidence of genetic decanalization relative to 22 low-altitude populations. Using these populations, we tested if these populations also var-23 ied for environmental canalization. We reared strains derived from these populations under 24 different temperature rearing environments. Using the Drosophila wing, we quantified size, 25 shape, cell density and frequencies of mutational defects. We observed the expected differ-26 ences in size, shape, cell density and mutational defects between the high-and low-altitude 27 populations. However, we observed little evidence for a relationship between a number of 28 measures of environmental canalization with population of origin or visible defect frequency. 29Our results do not support the predicted association between genetic and environmental 30 canalization. 31