This dissertation is the first critical analysis of patterns of species diversity in a deep-sea taxon (the Gastropoda) on a global scale. My analysis is based on 85 epibenthic sled samples collected from soft sediments in ten deep-sea regions of the Norwegian Sea and Atlantic Ocean. Over 21,000 gastropod individuals were sorted to species and their mode of larval development was documented. The basins from which the samples were taken represent a broad range of ecological circumstances that may affect species diversity and taxonomic composition. Bathymetric patterns of species diversity were shown to vary significantly among deep-sea basins. Unusually high or low values of diversity appear to be associated with environmental disturbance or rates of nutrient input. The most important and unexpected finding was that on a global scale there are latitudinal gradients in deep-sea species diversity similar to those in shallow-water and terrestrial environments. Gastropods show a clear and highly significant latitudinal decrease in diversity from the equator to 77$\sp\circ$N in the North Atlantic and a significant decrease from the equator to 37$\sp\circ$S in the South Atlantic. Depressed diversity at higher latitudes in the deep-sea, in part, may be related to seasonal nutrient loading and frequent physical disturbance from bottom currents. At lower latitudes, these same ecological factors may become less intense and variable. A multiple regression analysis showed that the North Atlantic local (sample) diversity is highly correlated with regional (basin) diversity suggesting that evolutionary-historical processes play a role in the development of deep-sea diversity through the mechanism of regional species enrichment. The percentage of species with planktotrophic development in the regional species pool was also correlated with local diversity. For the South Atlantic, the pattern of latitudinal diversity is less clear. On global scales, diversity gradients may be shaped by the interplay between the ecological potential and the history of evolutionary diversification at different latitudes. Underlying evolutionary processes that influence local diversity are difficult to recognize on a local scale, but may be revealed through large-scale patterns of species diversity. (Abstract shortened with permission of author.)
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-8448 |
| Date | 01 January 1991 |
| Creators | Stuart, Carol Tieslau |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
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