The Effects of Landscape Structure and Climate Change on the Movement, Connectivity, and Population Viability of the Hawaiian gallinule (Gallinula galeata sandvicensis)
van Rees, Charles.
Abstract: This dissertation examines the effects of anthropogenic landscape change on the population structure, functional connectivity, and extinction risk of the Hawaiian gallinule (Gallinula galeata sandvicensis), an endangered subspecies of waterbird endemic to Hawai`i. Through a combination of field work, population genetic analysis, geospatial analysis, simulation modeling, and meta-analysis ... read moreof published and unpublished work, I elucidate the behavioral and ecological mechanisms by which landscape structure impacts Hawaiian gallinule populations persisting on the island of O`ahu, Hawai`i. Hawaiian gallinules exhibited severe population declines throughout the late 19th to mid-20th century, a period coinciding with substantial development and reclamation of wetland habitat throughout Hawai`i. Their population on O`ahu has been slowly increasing since the late 1970's, and remaining populations persist in a fragmented, urbanized landscape. I quantified the extent of wetland loss across the archipelago, and investigated the population genetic impacts of this landscape fragmentation, as well as the recent population bottleneck, on the population structure of O`ahu's gallinule population. O`ahu had the greatest extent of wetland loss (in excess of 65%), concentrated particularly in the coastal lowlands, and sampled gallinule subpopulations across O`ahu showed moderately high genetic differentiation (overall microsatellite FST = 0.098, mtDNA FST = 0.248) across small spatial scales (1-35km). Using these genetic data, I tested a variety of biologically-informed movement hypotheses for how gallinules navigate the island's landscape. Models that treated water features like rivers, streams, and drainage canals as corridors for gallinule movement greatly outperformed other potential movement models across different molecular markers, simulation methods, and statistical tests. I next combined my own field observations with previous work from government reports, Masters theses and Doctoral dissertations to generate the first comprehensive review and estimation of the vital rates of Hawaiian gallinules. Finally, I used an individually-based, spatially explicit population model to explore the climate and landscape change impacts on the viability of O`ahu's gallinule population. Sensitivity analysis highlighted the importance of juvenile and adult survival for overall population persistence, and the importance of dispersal in mediating source-sink dynamics on the island. I estimated that O`ahu's major gallinule habitats could lose >40% of their carrying capacity under sea level rise conditions predicted for the next century.
Thesis (Ph.D.)--Tufts University, 2018.
Submitted to the Dept. of Biology.
Advisor: J. Michael Reed.
Committee: Elizabeth Crone, Colin Orians, Erik Dopman, and Brian Olsen.
Keywords: Conservation biology, Ecology, and Environmental management.read less