What is the symbolism behind the "marriage portrait" in the novel, The Marriage Portrait?

The author utilizes the marriage portrait as a symbol for the patriarchy. When the painting is complete, Lucrezia realizes that her corporeal presence is no longer necessary to Alfonso. The portrait serves as a trophy and evidence of their union, he does not need Lucrezia to continue his control of the duchy. The author utilizes this moment to signify that women are seen as disposable pawns for men in patriarchal political and cultural systems.