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Abstract
Ecological escalation (enemy-species driven selection) is thought to have played a primary role in the macroevolutionary patterns of marine invertebrates during the Mesozoic. The escalation hypothesis posits that taxonomic groups that can adapt to intense predation and bioturbation proliferate, whereas groups unable to adapt are reduced in diversity and abundance or driven to extinction. This dissertation tests the role of escalation on global diversity by testing for evidence of escalation during the Jurassic at different geographic scales and different environments. Using a combination of field-collected data and global data from the Paleobiology Database, the proportions of taxa with traits sensitive to escalation are tracked across Jurassic stages and compared between regions to test 1) the global extent of Jurassic escalation, 2) the role of environmental factors on escalation by comparing data among regions, and 3) test for variation of escalation within a single region. The first test tracks the proportional trajectory of taxonomic occurrences with nine ecological traits throughout the Jurassic in five difference regions parsed from global data (Europe, North America, South America, New Zealand, and Middle East). The second test focuses on the role of environmental factors, by comparing field data from the Middle Jurassic Carmel Formation in Utah, U.S.A., which was prone to poor environmental conditions (i.e., sluggish circulation, low-oxygen, hypersaline) with European data from conditions that were optimal to promote escalation. The third test attempts to find an escalation gradient that parallels a taxonomic diversity and environmental gradient within the Middle Jurassic Sundance Seaway in the western interior U.S. Results reveal that evidence of escalation is strongest in Europe and driven largely by optimal environmental conditions. Environmental conditions in the Carmel Formation hindered escalatory interactions, and despite a taxonomic diversity and environmental gradient in the Sundance Seaway, evidence of escalation is not present. The results of this dissertation underline the fact that while biotic factors may drive some macroevolutionary patterns, the development of these factors may depend on particular physical environmental conditions. Furthermore, these results reveal the importance of comparing paleoecological data across different geographic scales to understand the driving factors of macroevolutionary patterns.