Portland State University. Department of Geology
Michael L. Cummings
Date of Award
Master of Science (M.S.) in Geology
1 online resource (x, 130 p.) : ill. (some col.), maps (some col.)
Paleontology -- Pacific Northwest -- Miocene, Mammals -- Speciation -- Pacific Northwest, Mammals -- Evolution -- Pacific Northwest
The impact of large-scale volcanic eruptions on landscapes can affect many processes ranging from interrupting or redirecting regional soil forming processes and hydrological systems to generating temporary changes in global climate. Though more studies exist every year, less is known of the direct impact of large-scale volcanic eruptions on ecosystems and extinction, while even less is known of their impact on speciation. In deposits throughout the Pacific Northwest a special combination and association of volcanic magnitude with palaeoecological yield frequently presents unique prospects for inquiry. In this study, particular attention is given to large, late Miocene ash-flow tuffs of central and eastern Oregon, the Rattlesnake Tuff among them. Additionally, a scenario is tested whereby populations become isolated from one another across the expanse of ash-flow tuff and enclosed by nearby physical barriers. Exploration into this scenario and the effects of ecological recovery on speciation in mammals are made through a cellular automaton created here and speciation modeling by H.A. Orr. The cellular automaton is validated by a small data set from New Zealand with results of all models compared to studies in ecology, the fossil record, genetics, and island evolution. Results suggest ecosystem recovery is much faster than mammalian species origination rates. Though evolution in mammals is known to occur over relatively short intervals of time (10 - 10 yrs), based on model comparisons, primary productivity generally returns to its carrying capacity two orders of magnitude (10 - 10 vs. ≥ 10 yrs) faster than mammalian speciation.
McKenna, Ryan Thomas, "Potential for Speciation in Mammals Following Vast, Late Miocene Volcanic Interruptions in the Pacific Northwest" (2011). Dissertations and Theses. Paper 726.