First Advisor

McGlaughlin, Mitchell

Degree Name

Master of Science

Document Type

Thesis

Date Created

12-2018

Department

College of Natural and Health Sciences, Biological Sciences, Biological Sciences Student Work

Abstract

The Hawaiian Silversword Alliance (HSA) is a group of approximately 35 endemic species found on the Hawaiian Islands. The HSA is of particular interest due to the vast adaptive responses of its members across the Hawaiian Islands. Each of these plant species is generally limited to a very specific habitat type with a unique morphology and physiology. Dubautia scabra is the first angiosperm colonist of new lava flows, arriving in as few as two years after lava cools. The critical role D. scabra plays in this ecosystem gives a unique starting point for understanding downstream ecological processes such as seed dispersal, colonization, and ecological succession. The processes of colonization and ecological succession are widely understood by ecologists in habitats like forests and grasslands, but researchers have not yet been able to successfully characterize primary succession on truly new habitats. The goals of this study were to (1) characterize patterns of primary succession in new habitats, (2) determine if there is a correlation between lava flow age and genetic variation among populations, and (3) determine the source and direction of seed dispersal of D. scabra populations across the Big Island, Hawaii using genetic analysis. Regression analysis showed a negative correlation (R² = 0.4439) between lava flow age and plant size, and a positive correlation (R² = 0.7692) between lava flow age and plant density. The largest individuals were found on lava flows of about 100 years of age, with the most individuals found on lava flows between 40 and 45 years of age. Lava flow age, elevation, aspect, rock type, soil hydrology, and mean annual rainfall were also found to be ecological predictors of plant size and density on lava flows. There was no correlation between genetic divergence and lava flow age within populations found on The Big Island, which suggests frequent gene flow and migration events between all populations. Levels of inbreeding were found to decrease over time, and populations on lava flows of about 150 years of age had the least amount of inbreeding. Overall genetic diversity resembled that of other species within the Dubautia genus, but measures of genetic divergence were low between populations of D. scabra compared to other species within the HSA. The population at Saddle Road clustered genetically and therefore might be the source population that founded the other populations at Hawaii Volcanoes National Park and Hawaiian Ocean View Estates. Ecological and genetic analysis of organisms such as D. scabra give researchers the ability to identify patterns of colonization into new habitats, as well as determine the relationships within and among populations in other systems.

Extent

95 pages

Local Identifiers

NaibauerThesis2018.pdf

Rights Statement

Copyright is held by the author.

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