Is the genotype-phenotype map modular? : A statistical approach using mouse quantitative trait loci data

Various theories about the evolution of complex characters make predictions about the statistical distribution of genetic effects on phenotypic charac ters, also called the genotype-phenotype map. With the advent of QTL techno logy, data about these distributions are becoming available. In this articl e, we propose simple tests for the prediction that functionally integrated characters have a modular genotype-phenotype map. The test is applied to QT L data on the mouse mandible. The results provide statistical support for t he notion that the ascending ramus region of the mandible is modularized. A data set comprising the effects of QTL on a more extensive portion of the phenotype is required to determine if the alveolar region of the mandible i s also modularized.