A fundamental question of long standing in the study of life on Earth is, “Why
are there so many species?” This question concerns the distribution of and relationships
among species in the present day, but also requires an understanding of the history of
diversity. Patterns of diversity result from multiple, interconnected ecological processes
operating at different spatial scales. The goal of this research is to gain knowledge about
processes that control diversity by using fossil data to provide a temporal perspective
that is unavailable when studying modern ecological communities. The fossil record
provides the only natural historical account of changes in the diversity of ecological
communities in Earth’s past.
This research examines the taxonomic composition and diversity of brachiopod
paleocommunities in the Delaware Basin of west Texas (Guadalupe Mountains National
Park). The study interval is the Bell Canyon Formation, a 5.4-Myr interval of upper
Middle Permian (Capitanian) siliciclastic and carbonate rocks deposited on the toe-ofslope
of the basin. Silicified brachiopods extracted from the carbonate rocks provide the basis to test two hypotheses: (1) the taxonomic composition of local fossil brachiopod
paleocommunities remains uniform, and (2) the changes in diversity of local fossil
brachiopod paleocommunities reflects the relative importance of regional processes.
Multivariate analyses of clustering analysis and ordination, diversity partitioning, and
rank abundance plots are used to evaluate brachiopod taxonomic composition and
diversity within an ecological framework. Sequence stratigraphic analysis provides the
means to place the results within an environmental context related to sea-level changes.
Results indicate that the reorganization of brachiopod paleocommunity structure
coincides with major basinal-scale disruptions. Large disruptions allowed rare taxa and
invaders from outside the basin to become dominant within paleocommunities. The
dynamics within paleocommunities do not appear to prevent the replacement of the
incumbent taxa with new taxa. The importance of these findings indicate that
paleocommunities are not static through this interval and can be perturbed into
configurations with new dominant taxa. Therefore, ecological responses of
paleocommunities are resolvable at the geological time scale.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2010-08-8265 |
| Date | 2010 August 1900 |
| Creators | Fall, Leigh Margaret |
| Contributors | Olszewski, Thomas D. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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