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The Synergistic Effects of Environmental Change on the Population Dynamics of Localized Endemic Species, a Case Study in Hawai‘i.
|Title:||The Synergistic Effects of Environmental Change on the Population Dynamics of Localized Endemic Species, a Case Study in Hawai‘i.|
|Date Issued:||May 2017|
|Publisher:||University of Hawaiʻi at Mānoa|
|Abstract:||The spatial distribution and abundance of organisms are shaped by interactions with the environment. Human-induced changes in the environment can have varying effects on plant vital rates across ontogeny, sometimes in opposite directions. It is commonly thought that plant endangerment is the result of the combined effects of multiple environmental stressors. The influences of environmental stressors on components of plant fitness have been well examined. Few studies, however, have explicitly evaluated the synergistic effects of environmental stressors on the geospatial distribution of endangered species. In this dissertation I examined the population dynamics of three Hawaii endangered plants, Schiedea obovata, Cyrtandra dentata, and Delissea waianaeensis. Furthermore, I used a combination of size and stage structured demographic models to quantify the individual and combined impacts of dominant non-native pests and changing abiotic conditions on plant dynamics. I also compared the economic costs of various restoration strategies, including the suppression of non-native frugivores and seedling herbivores. I found that for S. obovata and C. dentata, fine-scale changes in microhabitat heterogeneity and inter-annual precipitation patterns had a greater effect on plant dynamics than top-down stressors. Furthermore, I found that the endangered plant populations were not always at, or close to, their equilibrium state (i.e., stable stage distribution SSD). There are many factors that contributed to the populations moving away from equilibrium, including population augmentation and the suppression of non-native pests. For the D. waianaeensis and C. dentata populations, there was a greater proportion of individuals in later life stages than would be expected if the populations were at a stable equilibrium. High reproductive value of these populations|
caused them to grow faster in the near-term transient phase (i.e., 10 years) than over the long-term as the population reached equilibrium (i.e., transient amplification). Furthermore, I found that there were numerous combinations of restoration actions that would likely shift the growth rate of endangered species from declining to growing. However, the yearly economic costs of targeted restoration actions were highly variable. From a global perspective, this study illustrates that changing precipitation patterns and alterations in microhabitat can have a greater negative impact on plant dynamics than non-native frugivores and seedling herbivores and thus should be considered when developing rare plant restoration strategies. This research also emphasizes how important it is to evaluate both the near term transient and asymptotic dynamics of endangered species in order to fully capture the likely outcome of restoration effort
|Description:||Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017.|
|Rights:||All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.|
|Appears in Collections:||
Ph.D. - Botany|
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