Using trait-based approaches to analyze the factors affecting theropod paleoecology in the Mesozoic.

摘要

A central tenet in studies attempting to understand dinosaur biodiversity from the deep time perspective of the fossil record focuses on documenting the interaction between changing morphology and ecology. If morphology can be summarized as the product of the interaction between phylogeny, ecology and stochastic processes, then evaluating the relative contributions of each to biological form is one approach to discerning potential ecologic relationships and interactions. Assessing these types of relationships will help us understand the processes driving biodiversity by clarifying the rules governing ecologic community organization among dinosaur species. It would help resolve lingering questions about how an ecosystem of substantially larger animals was able to coexist spatially and temporally and how different dinosaur communities were from mammalian ones. In this dissertation, I present an assessment of the factors that impacted theropod dinosaur ecology including taxonomic composition of the ecosystem, changes in morphology between and within clades through time, and the possible effects of ontogenetic change on niche occupation. I initially illustrated the changing patterns of ecosystem composition by looking at fossil occurrences and illustrated a pattern of passive replacement among the various dinosaur clades. Testing for selection-driven changes in morphological disparity, I found that increases in community variance drive changes in morphology and that theropods appear to all converge on the same general bauplan, suggesting that factors other than interspecific competition drive ecosystem structure between species. I also show that morphologic change through ontogeny played an important role in selecting for juvenile performance, which would have allowed immature individuals to coexist and acquire resources with larger, more mature individuals. These results suggest that both passive, within lineage factors as well as some extrinsic forces influenced theropod ecology and biodiversity.