DISSERTATION RESEARCH: The Evolution of Morphological Integration in the Mammalian Skull

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Abstract For DEB-0308765A grant has been awarded to Dr. John Flynn and Ms. Anjali Goswami of the University of Chicago, for a study of the evolution of morphological integration in the mammalian skull. The study of morphological integration examines sets of traits that are tightly correlated with each other, often due to similarity in function (e.g., diet, braincase), environmental adaptations, or developmental history. However, these sets of traits have never been studied for their consistency across more inclusive groups of organisms, over geological time, or for their influence on skull evolution. This research explores the relationships between parts of the skull, in their anatomy and developmental patterns, in both living and fossil species. A wide range of species from the mammalian orders Carnivora (dogs, cats, etc.), Primates (lemurs, apes, etc.), and Marsupialia (opposums, kangaroos, etc.) are used to examine patterns of integration and to assess the influence of three key factors: 1) diet, 2) brain size, and 3) reproductive strategy, on the relationships among skull traits and diversity of form. Developmental integration is explored through analysis of the order in which skull bones form. Morphological integration is examined through statistical analysis of correlations among skull landmarks, captured using a high-accuracy 3D digitizer.This study bridges a long-standing gap between the fields of genetics, development, and paleontology. Developmental and genetic studies have produced many hypotheses of the importance of the correlated evolution of traits, but these have never been tested. Using the extensive fossil record of mammals and diverse collections representing all stages of development, this study addresses questions about diversity, morphology, and the flexibility of the evolutionary process, which are crucial to understanding the ability of organisms to adapt to environmental change. This research also should shed light on the consequences and primary factors in human craniofacial disorders, such as craniosyntosis.