Thesis
Effect of Specialist herbivores on a keystone plant facilitator in volcanic primary succession persist for decades and recur on recently initiated surfaces
Washington State University
Master of Science (MS), Washington State University
2018
Handle:
https://hdl.handle.net/2376/102713
Abstract
The ability of herbivores to regulate plant communities is generally appreciated but thought to be unimportant in recently-initiated communities. However, herbivory on Lupinus lepidus (alpine lupin), a keystone facilitator on Mount St. Helens volcano, Washington, USA, was previously demonstrated to depress its colonization rate and thereby delay soil and community development in the first 13-20 years of primary succession. We investigate whether the negative effects of specialist insect herbivores (leaf-miners) on L. lepidus population dynamics observed in the 1990s continued, and whether those effects would recur when primary succession. To do this we used 20 years of observational survey data (years 18-38 of succession) and conducted a 4-year herbivore removal experiment in a young (2006-initiated) primary successional community. As in previous research in this system, leaf-miner damage was severe in low-density areas, exceeding 60% defoliation in the 2006-initiated control plots, and inversely proportional to lupin cover, with damage <1% in high-density areas. Exclusion of herbivores from 2006-initiated surfaces resulted in a 3x increase in lupin cover by year 3. However, in contrast to observations two decades earlier, lupins colonized bare surfaces in 2006-initiated sites more quickly, colonizing all areas in only 5 years compared to >20 following the 1980 eruption. In addition, leaf-miners more rapidly found newly colonizing lupin in 2006-initiated sites than 20 years earlier. Finally, a previously unobserved soil pathogen caused wide-spread mortality of adult lupins in 2016 across the entire study area and a consequent collapse of specialist leaf miners in 2017. Both observational and experimental data indicate that insect herbivores that specialize on keystone facilitators at low densities still have a strong negative effect in newly-developing communities on Mount St. Helens. Further, that effect appears to depend on the spatial scale of disturbances generating primary successional habitat. Proximity of the 2006-initiated surfaces to a more-developed meta-community than was present in the 1990s may enable more rapid colonization by both lupins and their specialist herbivores and introduce new species interactions that may diminish insect herbivore effects compared to when the plant-herbivore interaction occurred in relative isolation.
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Details
- Title
- Effect of Specialist herbivores on a keystone plant facilitator in volcanic primary succession persist for decades and recur on recently initiated surfaces
- Creators
- James Roy Moore
- Contributors
- John G. Bishop (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Biological Sciences, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525185101842
- Language
- English
- Resource Type
- Thesis