Evidence for canalization of Distal-less function in the leg of Drosophila melanogaster.

A considerable body of theory pertaining to the evolution of canalization has emerged recently, yet there have been few empirical investigations of their predictions. To address this, patterns of canalization and trait correlation were investigated under the individual and joint effects of the introgression of a loss-of-function allele of the Distal-less gene and high-temperature stress on a panel of iso-female lines. Variation was examined for number of sex comb teeth and the length of the basi-tarsus on the pro-thoracic leg of male Drosophila melanogaster. I demonstrate that whereas there is evidence for trait canalization, there is no evidence to support the hypothesis of the evolution of genetic canalization as a response to microenvironmental canalization. Furthermore, I demonstrate that although there are genetic correlations between these traits, there is no association between their measures of canalization. I discuss the prospects of the evolutionary lability of the Distal-less gene within the context of changes in genetic variation and covariation.