CONICET | Buscador de Institutos y Recursos Humanos

To predict the response of complex morphological structures to selection it is necessary to know how the covariation among itsdifferent parts is organized. Two key features of covariation are modularity and integration. The Drosophila wing is currentlyconsidered a fully integrated structure. Here, we study the patterns of integration of the Drosophila wing and test the hypothesisof the wing being divided into two modules along the proximo-distal axis, as suggested by developmental, biomechanical,and evolutionary evidence. To achieve these goals we perform a multilevel analysis of covariation combining the techniques ofgeometric morphometrics and quantitative genetics. Our results indicate that the Drosophila wing is indeed organized into twomain modules, the wing base and the wing blade. The patterns of integration and modularity were highly concordant at thephenotypic, genetic, environmental, and developmental levels. Besides, we found that modularity at the developmental level wasconsiderably higher than modularity at other levels, suggesting that in the Drosophila wing direct developmental interactionsare major contributors to total phenotypic shape variation. We propose that the precise time at which covariance-generatingdevelopmental processes occur and/or the magnitude of variation that they produce favor proximo-distal, rather than anteriorposterior,modularity in the Drosophila wing.